feat(datetime): resolve datetime TODOs

Introduce shim functions and constants, replacing the ad-hoc chrono
format strings and parse helpers used as phase-b placeholders.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

23 files changed, 189 insertions, 159 deletions

diff --git a/crates/shirabe-php-shim/Cargo.toml b/crates/shirabe-php-shim/Cargo.toml
index 30e132f..b2a2077 100644
--- a/crates/shirabe-php-shim/Cargo.toml
+++ b/crates/shirabe-php-shim/Cargo.toml
@@ -5,6 +5,7 @@ edition.workspace = true
 
 [dependencies]
 anyhow.workspace = true
+chrono.workspace = true
 indexmap.workspace = true
 serde.workspace = true
 zip.workspace = true
diff --git a/crates/shirabe-php-shim/src/lib.rs b/crates/shirabe-php-shim/src/lib.rs
index 835e1c1..433b8db 100644
--- a/crates/shirabe-php-shim/src/lib.rs
+++ b/crates/shirabe-php-shim/src/lib.rs
@@ -1740,8 +1740,6 @@ pub fn abs(_value: i64) -> i64 {
     todo!()
 }
 
-pub const DATE_ATOM: &str = "Y-m-d\\TH:i:sP";
-
 pub fn ucfirst(_s: &str) -> String {
     todo!()
 }
@@ -2409,7 +2407,6 @@ pub const OPENSSL_VERSION_NUMBER: i64 = 0;
 pub const OPENSSL_VERSION_TEXT: &str = "";
 pub const PHP_BINARY: &str = "";
 pub const PHP_WINDOWS_VERSION_BUILD: i64 = 0;
-pub const DATE_RFC3339: &str = "Y-m-d\\TH:i:sP";
 pub const PREG_BACKTRACK_LIMIT_ERROR: i64 = 2;
 
 #[derive(Debug, Clone)]
@@ -2459,3 +2456,24 @@ pub fn zlib_decode(_data: &str) -> Option<String> {
 pub const STREAM_NOTIFY_FAILURE: i64 = 9;
 pub const STREAM_NOTIFY_FILE_SIZE_IS: i64 = 5;
 pub const STREAM_NOTIFY_PROGRESS: i64 = 7;
+
+pub fn date_create<Tz: chrono::TimeZone>(s: &str) -> chrono::ParseResult<chrono::DateTime<Tz>> {
+    todo!()
+}
+
+/// PHP: \DATE_RFC3339 ("Y-m-d\TH:i:sP").
+pub const DATE_RFC3339: &str = "%Y-%m-%dT%H:%M:%S%:z";
+
+/// PHP: \DATE_ATOM (equivalent to \DATE_RFC3339).
+pub const DATE_ATOM: &str = DATE_RFC3339;
+
+/// Convert PHP-compatible date time format to strftime-compatible format.
+/// Only the patterns Composer actually passes are supported; anything else panics.
+pub fn date_format_to_strftime(format: &str) -> &'static str {
+    match format {
+        "Y-m-d H:i:s" => "%Y-%m-%d %H:%M:%S",
+        "Y-m-d" => "%Y-%m-%d",
+        "Ymd" => "%Y%m%d",
+        other => panic!("Unsupported PHP date format: {other:?}"),
+    }
+}
diff --git a/crates/shirabe/src/advisory/auditor.rs b/crates/shirabe/src/advisory/auditor.rs
index 179278a..2b71237 100644
--- a/crates/shirabe/src/advisory/auditor.rs
+++ b/crates/shirabe/src/advisory/auditor.rs
@@ -6,8 +6,8 @@ use indexmap::IndexMap;
 use shirabe_external_packages::composer::pcre::Preg;
 use shirabe_external_packages::symfony::console::formatter::OutputFormatter;
 use shirabe_php_shim::{
-    InvalidArgumentException, PhpMixed, array_all, array_any, array_key_exists, array_keys,
-    array_reduce, get_class, sprintf, str_starts_with,
+    DATE_ATOM, InvalidArgumentException, PhpMixed, array_all, array_any, array_key_exists,
+    array_keys, array_reduce, get_class, sprintf, str_starts_with,
 };
 
 use crate::advisory::AnySecurityAdvisory;
@@ -464,11 +464,7 @@ impl Auditor {
                     sa.title.clone(),
                     self.get_url(sa),
                     sa.affected_versions().get_pretty_string(),
-                    // TODO(phase-b): PHP uses `$advisory->reportedAt->format(DATE_ATOM)`, but
-                    // shim DATE_ATOM ("Y-m-d\TH:i:sP") is a PHP format string incompatible with
-                    // chrono. Using the chrono equivalent directly; revisit once a PHP-style date
-                    // formatter exists (see also locker.rs DATE_RFC3339).
-                    sa.reported_at.format("%Y-%m-%dT%H:%M:%S%:z").to_string(),
+                    sa.reported_at.format(DATE_ATOM).to_string(),
                 ];
                 if let Some(ignored) = advisory.as_ignored() {
                     headers.push("Ignore reason".to_string());
@@ -523,14 +519,7 @@ impl Auditor {
                     "Affected versions: {}",
                     OutputFormatter::escape(&sa.affected_versions().get_pretty_string())
                 ));
-                error.push(format!(
-                    "Reported at: {}",
-                    // TODO(phase-b): PHP uses `$advisory->reportedAt->format(DATE_ATOM)`, but
-                    // shim DATE_ATOM ("Y-m-d\TH:i:sP") is a PHP format string incompatible with
-                    // chrono. Using the chrono equivalent directly; revisit once a PHP-style date
-                    // formatter exists (see also locker.rs DATE_RFC3339).
-                    sa.reported_at.format("%Y-%m-%dT%H:%M:%S%:z")
-                ));
+                error.push(format!("Reported at: {}", sa.reported_at.format(DATE_ATOM)));
                 if let Some(ignored) = advisory.as_ignored() {
                     error.push(format!(
                         "Ignore reason: {}",
diff --git a/crates/shirabe/src/advisory/partial_security_advisory.rs b/crates/shirabe/src/advisory/partial_security_advisory.rs
index 2062570..f72ecaa 100644
--- a/crates/shirabe/src/advisory/partial_security_advisory.rs
+++ b/crates/shirabe/src/advisory/partial_security_advisory.rs
@@ -4,10 +4,10 @@ use crate::advisory::AnySecurityAdvisory;
 use crate::advisory::SecurityAdvisory;
 use crate::package::version::VersionParser;
 use anyhow::Result;
-use chrono::{DateTime, TimeZone, Utc};
+use chrono::{DateTime, Utc};
 use indexmap::IndexMap;
 use shirabe_external_packages::composer::pcre::Preg;
-use shirabe_php_shim::{PhpMixed, UnexpectedValueException};
+use shirabe_php_shim::{DATE_RFC3339, PhpMixed, UnexpectedValueException};
 use shirabe_semver::constraint::AnyConstraint;
 use shirabe_semver::constraint::SimpleConstraint;
 
@@ -57,12 +57,9 @@ impl PartialSecurityAdvisory {
             && data.contains_key("reportedAt");
 
         if has_full_data {
-            let reported_at: DateTime<Utc> = Utc
-                .datetime_from_str(
-                    data["reportedAt"].as_string().unwrap_or(""),
-                    "%Y-%m-%dT%H:%M:%S+00:00",
-                )
-                .unwrap_or_default();
+            let reported_at: DateTime<Utc> =
+                shirabe_php_shim::date_create(data["reportedAt"].as_string().unwrap_or(""))
+                    .unwrap_or_default();
             let sources: Vec<IndexMap<String, String>> = data["sources"]
                 .as_list()
                 .map(|list| {
diff --git a/crates/shirabe/src/advisory/security_advisory.rs b/crates/shirabe/src/advisory/security_advisory.rs
index 2c5a309..7c258ee 100644
--- a/crates/shirabe/src/advisory/security_advisory.rs
+++ b/crates/shirabe/src/advisory/security_advisory.rs
@@ -2,17 +2,17 @@
 
 use chrono::{DateTime, Utc};
 use indexmap::IndexMap;
+use shirabe_php_shim::DATE_RFC3339;
 use shirabe_semver::constraint::AnyConstraint;
 
 use crate::advisory::IgnoredSecurityAdvisory;
 use crate::advisory::PartialSecurityAdvisory;
 
-/// Matches PHP's `format(DATE_RFC3339)`, e.g. "2020-01-01T00:00:00+00:00".
 fn serialize_date_rfc3339<S: serde::Serializer>(
     dt: &DateTime<Utc>,
     serializer: S,
 ) -> Result<S::Ok, S::Error> {
-    serializer.serialize_str(&dt.format("%Y-%m-%dT%H:%M:%S%:z").to_string())
+    serializer.serialize_str(&dt.format(DATE_RFC3339).to_string())
 }
 
 #[derive(Debug, Clone, serde::Serialize)]
diff --git a/crates/shirabe/src/cache.rs b/crates/shirabe/src/cache.rs
index 1a1f67f..74e3c15 100644
--- a/crates/shirabe/src/cache.rs
+++ b/crates/shirabe/src/cache.rs
@@ -7,8 +7,9 @@ use chrono::Utc;
 use shirabe_external_packages::composer::pcre::Preg;
 use shirabe_external_packages::symfony::finder::Finder;
 use shirabe_php_shim::{
-    abs, bin2hex, dirname, file_exists, file_get_contents, file_put_contents, filemtime, hash_file,
-    is_dir, is_writable, mkdir, random_bytes, random_int, rename, time, unlink,
+    abs, bin2hex, date_format_to_strftime, dirname, file_exists, file_get_contents,
+    file_put_contents, filemtime, hash_file, is_dir, is_writable, mkdir, random_bytes, random_int,
+    rename, time, unlink,
 };
 
 use crate::io::IOInterface;
@@ -278,12 +279,13 @@ impl Cache {
 
     pub fn gc(&mut self, ttl: i64, max_size: i64) -> bool {
         if self.is_enabled() && !self.read_only {
-            let mut expire = Utc::now();
-            // PHP: $expire->modify('-'.$ttl.' seconds');
-            expire -= chrono::Duration::seconds(ttl);
+            let expire = Utc::now() - chrono::Duration::seconds(ttl);
 
             let mut finder = self.get_finder();
-            finder.date(&format!("until {}", expire.format("%Y-%m-%d %H:%M:%S")));
+            finder.date(&format!(
+                "until {}",
+                expire.format(date_format_to_strftime("Y-m-d H:i:s"))
+            ));
             for file in &mut finder {
                 let _ = self.filesystem.borrow_mut().unlink(&file.get_pathname());
             }
@@ -309,15 +311,17 @@ impl Cache {
 
     pub fn gc_vcs_cache(&mut self, ttl: i64) -> bool {
         if self.is_enabled() {
-            let mut expire = Utc::now();
-            expire -= chrono::Duration::seconds(ttl);
+            let expire = Utc::now() - chrono::Duration::seconds(ttl);
 
             let mut finder = Finder::create();
             finder
                 .r#in(&self.root)
                 .directories()
                 .depth(0)
-                .date(&format!("until {}", expire.format("%Y-%m-%d %H:%M:%S")));
+                .date(&format!(
+                    "until {}",
+                    expire.format(date_format_to_strftime("Y-m-d H:i:s"))
+                ));
             for file in &mut finder {
                 let _ = self
                     .filesystem
diff --git a/crates/shirabe/src/command/show_command.rs b/crates/shirabe/src/command/show_command.rs
index e99005e..7ee103a 100644
--- a/crates/shirabe/src/command/show_command.rs
+++ b/crates/shirabe/src/command/show_command.rs
@@ -9,8 +9,9 @@ use shirabe_external_packages::symfony::console::formatter::OutputFormatterStyle
 use shirabe_external_packages::symfony::console::input::InputInterface;
 use shirabe_external_packages::symfony::console::output::OutputInterface;
 use shirabe_php_shim::{
-    InvalidArgumentException, LogicException, PhpMixed, UnexpectedValueException, array_search,
-    date, extension_loaded, in_array, realpath, strtolower, version_compare,
+    DATE_ATOM, InvalidArgumentException, LogicException, PhpMixed, UnexpectedValueException,
+    array_search, date, date_format_to_strftime, extension_loaded, in_array, realpath, strtolower,
+    version_compare,
 };
 
 use shirabe_semver::constraint::AnyConstraint;
@@ -1026,7 +1027,7 @@ impl ShowCommand {
                                     .insert("release-age".to_string(), PhpMixed::String(age));
                                 package_view_data.insert(
                                     "release-date".to_string(),
-                                    PhpMixed::String(release_date.to_rfc3339()),
+                                    PhpMixed::String(release_date.format(DATE_ATOM).to_string()),
                                 );
                             } else {
                                 package_view_data.insert(
@@ -1062,7 +1063,7 @@ impl ShowCommand {
                             if let Some(rd) = latest.get_release_date() {
                                 package_view_data.insert(
                                     "latest-release-date".to_string(),
-                                    PhpMixed::String(rd.to_rfc3339()),
+                                    PhpMixed::String(rd.format(DATE_ATOM).to_string()),
                                 );
                             } else {
                                 package_view_data.insert(
@@ -1666,7 +1667,7 @@ impl ShowCommand {
                 let rel = self.get_relative_time(&rd);
                 self.get_io().write(&format!(
                     "<info>released</info> : {}, {}",
-                    rd.format("%Y-%m-%d"),
+                    rd.format(date_format_to_strftime("Y-m-d")),
                     rel
                 ));
             }
@@ -1677,7 +1678,11 @@ impl ShowCommand {
                 None => String::new(),
                 Some(rd) => {
                     let rel = self.get_relative_time(&rd);
-                    format!(" released {}, {}", rd.format("%Y-%m-%d"), rel)
+                    format!(
+                        " released {}, {}",
+                        rd.format(date_format_to_strftime("Y-m-d")),
+                        rel
+                    )
                 }
             };
             self.get_io().write(&format!(
@@ -2017,7 +2022,10 @@ impl ShowCommand {
             }
 
             if let Some(rd) = package.get_release_date() {
-                json.insert("released".to_string(), PhpMixed::String(rd.to_rfc3339()));
+                json.insert(
+                    "released".to_string(),
+                    PhpMixed::String(rd.format(DATE_ATOM).to_string()),
+                );
             }
         }
 
@@ -2786,12 +2794,15 @@ impl ShowCommand {
     }
 
     fn get_relative_time(&self, release_date: &chrono::DateTime<chrono::Utc>) -> String {
-        if release_date.format("%Y%m%d").to_string() == date("Ymd", None) {
+        if release_date
+            .format(date_format_to_strftime("Ymd"))
+            .to_string()
+            == date("Ymd", None)
+        {
             return "today".to_string();
         }
 
-        let now: chrono::DateTime<chrono::Utc> = chrono::Utc::now();
-        let diff = now.signed_duration_since(*release_date);
+        let diff = chrono::Utc::now().signed_duration_since(*release_date);
         let days = diff.num_days();
         if days < 7 {
             return "this week".to_string();
diff --git a/crates/shirabe/src/compiler.rs b/crates/shirabe/src/compiler.rs
index 1088477..05177d6 100644
--- a/crates/shirabe/src/compiler.rs
+++ b/crates/shirabe/src/compiler.rs
@@ -9,8 +9,8 @@ use shirabe_external_packages::symfony::finder::Finder;
 use shirabe_external_packages::symfony::finder::SplFileInfo;
 use shirabe_php_shim::{
     Phar, PhpMixed, RuntimeException, T_COMMENT, T_DOC_COMMENT, T_WHITESPACE,
-    UnexpectedValueException, array_search, file_exists, file_get_contents, strcmp, strtr,
-    strtr_array, token_get_all,
+    UnexpectedValueException, array_search, date_format_to_strftime, file_exists,
+    file_get_contents, strcmp, strtr, strtr_array, token_get_all,
 };
 
 use crate::json::JsonFile;
@@ -95,8 +95,7 @@ impl Compiler {
         let version_date_str = Git::parse_rev_list_output(&output, &process);
         self.version_date =
             chrono::DateTime::parse_from_str(version_date_str.trim(), "%Y-%m-%d %H:%M:%S %z")
-                .map(|dt| dt.with_timezone(&chrono::Utc))
-                .unwrap_or_else(|_| chrono::Utc::now());
+                .map(|dt| dt.with_timezone(&chrono::Utc))?;
 
         let mut git_describe_output = String::new();
         if process.borrow_mut().execute_args(
@@ -298,7 +297,12 @@ impl Compiler {
 
         // re-sign the phar with reproducible timestamp / signature
         let mut util = Timestamps::new(phar_file);
-        util.update_timestamps(&self.version_date.format("%Y-%m-%d %H:%M:%S").to_string())?;
+        util.update_timestamps(
+            &self
+                .version_date
+                .format(date_format_to_strftime("Y-m-d H:i:s"))
+                .to_string(),
+        )?;
         util.save(phar_file, Phar::SHA512)?;
 
         Linter::lint(
@@ -355,7 +359,9 @@ impl Compiler {
             );
             replacements.insert(
                 "@release_date@".to_string(),
-                self.version_date.format("%Y-%m-%d %H:%M:%S").to_string(),
+                self.version_date
+                    .format(date_format_to_strftime("Y-m-d H:i:s"))
+                    .to_string(),
             );
             content = strtr_array(&content, &replacements);
             content = Preg::replace(
diff --git a/crates/shirabe/src/package/dumper/array_dumper.rs b/crates/shirabe/src/package/dumper/array_dumper.rs
index 4217308..27fc415 100644
--- a/crates/shirabe/src/package/dumper/array_dumper.rs
+++ b/crates/shirabe/src/package/dumper/array_dumper.rs
@@ -1,7 +1,7 @@
 //! ref: composer/src/Composer/Package/Dumper/ArrayDumper.php
 
 use indexmap::IndexMap;
-use shirabe_php_shim::PhpMixed;
+use shirabe_php_shim::{DATE_RFC3339, PhpMixed};
 
 use crate::package::Mirror;
 use crate::package::PackageInterfaceHandle;
@@ -156,7 +156,7 @@ impl ArrayDumper {
         if let Some(release_date) = package.get_release_date() {
             data.insert(
                 "time".to_string(),
-                PhpMixed::String(release_date.to_rfc3339()),
+                PhpMixed::String(release_date.format(DATE_RFC3339).to_string()),
             );
         }
 
diff --git a/crates/shirabe/src/package/loader/array_loader.rs b/crates/shirabe/src/package/loader/array_loader.rs
index d2aeac6..4df022b 100644
--- a/crates/shirabe/src/package/loader/array_loader.rs
+++ b/crates/shirabe/src/package/loader/array_loader.rs
@@ -1,12 +1,12 @@
 //! ref: composer/src/Composer/Package/Loader/ArrayLoader.php
 
 use anyhow::Result;
-use chrono::{DateTime, TimeZone, Utc};
+use chrono::Utc;
 use indexmap::IndexMap;
 use shirabe_external_packages::composer::pcre::Preg;
 use shirabe_php_shim::{
-    E_USER_DEPRECATED, Exception, PhpMixed, UnexpectedValueException, is_scalar, is_string,
-    json_encode, ltrim, sprintf, stripos, strpos, strtolower, strval, substr, trigger_error, trim,
+    E_USER_DEPRECATED, PhpMixed, UnexpectedValueException, is_scalar, is_string, json_encode,
+    ltrim, sprintf, stripos, strpos, strtolower, strval, substr, trigger_error, trim,
 };
 
 use crate::package::CompleteAliasPackageHandle;
@@ -527,14 +527,7 @@ impl ArrayLoader {
                     time_str.to_string()
                 };
 
-                let result: std::result::Result<DateTime<Utc>, Exception> =
-                    // TODO(phase-b): port PHP `new \DateTime($time, new \DateTimeZone('UTC'))`
-                    Utc.datetime_from_str(&time, "%Y-%m-%dT%H:%M:%S%z")
-                        .map_err(|e| Exception {
-                            message: e.to_string(),
-                            code: 0,
-                        });
-                if let Ok(date) = result {
+                if let Ok(date) = shirabe_php_shim::date_create::<Utc>(&time) {
                     package.package_mut().set_release_date(Some(date));
                 }
             }
diff --git a/crates/shirabe/src/package/loader/validating_array_loader.rs b/crates/shirabe/src/package/loader/validating_array_loader.rs
index 4994d5a..e6db19e 100644
--- a/crates/shirabe/src/package/loader/validating_array_loader.rs
+++ b/crates/shirabe/src/package/loader/validating_array_loader.rs
@@ -6,10 +6,10 @@ use indexmap::IndexMap;
 use shirabe_external_packages::composer::pcre::Preg;
 use shirabe_external_packages::composer::spdx_licenses::SpdxLicenses;
 use shirabe_php_shim::{
-    E_USER_DEPRECATED, Exception, FILTER_VALIDATE_EMAIL, PHP_EOL, PhpMixed, array_intersect_key,
-    array_values, filter_var, get_debug_type, is_array, is_bool, is_int, is_numeric, is_scalar,
-    is_string, json_encode, parse_url_all, php_to_string, sprintf, str_replace, strcasecmp,
-    strtolower, strtotime, substr, trigger_error, trim, var_export,
+    E_USER_DEPRECATED, FILTER_VALIDATE_EMAIL, PHP_EOL, PhpMixed, array_intersect_key, array_values,
+    filter_var, get_debug_type, is_array, is_bool, is_int, is_numeric, is_scalar, is_string,
+    json_encode, parse_url_all, php_to_string, sprintf, str_replace, strcasecmp, strtolower,
+    strtotime, substr, trigger_error, trim, var_export,
 };
 use shirabe_semver::constraint::AnyConstraint;
 use shirabe_semver::constraint::MatchNoneConstraint;
@@ -166,7 +166,7 @@ impl ValidatingArrayLoader {
         self.validate_string("time", false);
         if self.config.contains_key("time") {
             let time_str = self.config["time"].as_string().unwrap_or("").to_string();
-            match Self::parse_datetime_utc(&time_str) {
+            match shirabe_php_shim::date_create::<chrono::Utc>(&time_str) {
                 Ok(dt) => {
                     release_date = Some(dt);
                 }
@@ -1591,22 +1591,4 @@ impl ValidatingArrayLoader {
             None => true,
         }
     }
-
-    fn parse_datetime_utc(s: &str) -> anyhow::Result<chrono::DateTime<chrono::Utc>> {
-        // TODO(phase-b): PHP's `new \DateTime($s, new \DateTimeZone('UTC'))` accepts
-        // many free-form formats; approximate with chrono for now.
-        if let Ok(dt) = chrono::DateTime::parse_from_rfc3339(s) {
-            return Ok(dt.with_timezone(&chrono::Utc));
-        }
-        if let Ok(dt) = chrono::NaiveDateTime::parse_from_str(s, "%Y-%m-%d %H:%M:%S") {
-            return Ok(chrono::Utc.from_utc_datetime(&dt));
-        }
-        if let Ok(d) = chrono::NaiveDate::parse_from_str(s, "%Y-%m-%d") {
-            return Ok(chrono::Utc.from_utc_datetime(&d.and_hms_opt(0, 0, 0).unwrap()));
-        }
-        Err(anyhow::anyhow!(Exception {
-            message: format!("Failed to parse date: {}", s),
-            code: 0,
-        }))
-    }
 }
diff --git a/crates/shirabe/src/package/locker.rs b/crates/shirabe/src/package/locker.rs
index 5f13a31..2546780 100644
--- a/crates/shirabe/src/package/locker.rs
+++ b/crates/shirabe/src/package/locker.rs
@@ -876,7 +876,6 @@ impl Locker {
                             None,
                         );
                         if Preg::is_match(r"{^\s*\d+\s*$}", &output_str).unwrap_or(false) {
-                            // TODO(phase-b): new \DateTime('@'.trim($output), new \DateTimeZone('UTC'))
                             let ts = trim(&output_str, None).parse::<i64>().unwrap_or(0);
                             datetime = chrono::DateTime::from_timestamp(ts, 0);
                         }
diff --git a/crates/shirabe/src/repository/vcs/forgejo_driver.rs b/crates/shirabe/src/repository/vcs/forgejo_driver.rs
index a40f6a9..73975cd 100644
--- a/crates/shirabe/src/repository/vcs/forgejo_driver.rs
+++ b/crates/shirabe/src/repository/vcs/forgejo_driver.rs
@@ -5,7 +5,7 @@ use anyhow::Result;
 use indexmap::IndexMap;
 use shirabe_external_packages::composer::pcre::{CaptureKey, Preg};
 use shirabe_php_shim::{
-    PhpMixed, RuntimeException, base64_decode, explode, extension_loaded, urlencode,
+    DATE_RFC3339, PhpMixed, RuntimeException, base64_decode, explode, extension_loaded, urlencode,
 };
 
 use crate::cache::Cache;
@@ -185,7 +185,7 @@ impl ForgejoDriver {
     pub fn get_change_date(
         &mut self,
         identifier: &str,
-    ) -> Result<Option<chrono::DateTime<chrono::Utc>>> {
+    ) -> Result<Option<chrono::DateTime<chrono::FixedOffset>>> {
         if let Some(ref mut git_driver) = self.git_driver {
             return git_driver.get_change_date(identifier);
         }
@@ -218,8 +218,7 @@ impl ForgejoDriver {
             code: 0,
         })?;
 
-        let date = chrono::DateTime::parse_from_rfc3339(&date_str)
-            .map(|d| d.with_timezone(&chrono::Utc))?;
+        let date: chrono::DateTime<chrono::FixedOffset> = shirabe_php_shim::date_create(&date_str)?;
         Ok(Some(date))
     }
 
@@ -725,7 +724,7 @@ impl crate::repository::vcs::VcsDriverInterface for ForgejoDriver {
     fn get_change_date(
         &mut self,
         identifier: &str,
-    ) -> anyhow::Result<Option<chrono::DateTime<chrono::Utc>>> {
+    ) -> anyhow::Result<Option<chrono::DateTime<chrono::FixedOffset>>> {
         ForgejoDriver::get_change_date(self, identifier)
     }
 
diff --git a/crates/shirabe/src/repository/vcs/fossil_driver.rs b/crates/shirabe/src/repository/vcs/fossil_driver.rs
index 0ee20da..15328c0 100644
--- a/crates/shirabe/src/repository/vcs/fossil_driver.rs
+++ b/crates/shirabe/src/repository/vcs/fossil_driver.rs
@@ -1,10 +1,12 @@
 //! ref: composer/src/Composer/Repository/Vcs/FossilDriver.php
 
 use crate::io::io_interface;
-use chrono::{DateTime, Utc};
+use chrono::{DateTime, FixedOffset, Utc};
 use indexmap::IndexMap;
 use shirabe_external_packages::composer::pcre::Preg;
-use shirabe_php_shim::{PhpMixed, RuntimeException, dirname, is_dir, is_file, is_writable};
+use shirabe_php_shim::{
+    DATE_RFC3339, PhpMixed, RuntimeException, dirname, is_dir, is_file, is_writable,
+};
 
 use crate::cache::Cache;
 use crate::config::Config;
@@ -256,7 +258,10 @@ impl FossilDriver {
         Ok(Some(content))
     }
 
-    pub fn get_change_date(&self, _identifier: &str) -> anyhow::Result<Option<DateTime<Utc>>> {
+    pub fn get_change_date(
+        &self,
+        _identifier: &str,
+    ) -> anyhow::Result<Option<DateTime<FixedOffset>>> {
         let mut output = String::new();
         self.inner.process.borrow_mut().execute_args(
             &["fossil", "finfo", "-b", "-n", "1", "composer.json"]
@@ -268,8 +273,8 @@ impl FossilDriver {
         let parts: Vec<&str> = output.trim().splitn(3, ' ').collect();
         let date = parts.get(1).copied().unwrap_or("");
 
-        let date = DateTime::parse_from_rfc3339(date).map(|d| d.with_timezone(&Utc))?;
-        Ok(Some(date))
+        let date: DateTime<Utc> = shirabe_php_shim::date_create(date)?;
+        Ok(Some(date.fixed_offset()))
     }
 
     pub fn get_tags(&mut self) -> anyhow::Result<IndexMap<String, String>> {
@@ -383,7 +388,10 @@ impl crate::repository::vcs::VcsDriverInterface for FossilDriver {
         FossilDriver::get_file_content(self, file, identifier)
     }
 
-    fn get_change_date(&mut self, identifier: &str) -> anyhow::Result<Option<DateTime<Utc>>> {
+    fn get_change_date(
+        &mut self,
+        identifier: &str,
+    ) -> anyhow::Result<Option<DateTime<FixedOffset>>> {
         FossilDriver::get_change_date(self, identifier)
     }
 
diff --git a/crates/shirabe/src/repository/vcs/git_bitbucket_driver.rs b/crates/shirabe/src/repository/vcs/git_bitbucket_driver.rs
index f8cfd7a..de1f814 100644
--- a/crates/shirabe/src/repository/vcs/git_bitbucket_driver.rs
+++ b/crates/shirabe/src/repository/vcs/git_bitbucket_driver.rs
@@ -2,13 +2,13 @@
 
 use crate::io::io_interface;
 use anyhow::Result;
-use chrono::{DateTime, Utc};
+use chrono::{DateTime, FixedOffset};
 use indexmap::IndexMap;
 use shirabe_external_packages::composer::pcre::{CaptureKey, Preg};
 use shirabe_php_shim::{
-    InvalidArgumentException, LogicException, PhpMixed, RuntimeException, array_key_exists,
-    array_search_mixed, extension_loaded, http_build_query_mixed, implode, in_array, is_array,
-    sprintf, strpos,
+    DATE_RFC3339, InvalidArgumentException, LogicException, PhpMixed, RuntimeException,
+    array_key_exists, array_search_mixed, extension_loaded, http_build_query_mixed, implode,
+    in_array, is_array, sprintf, strpos,
 };
 
 use crate::cache::Cache;
@@ -461,7 +461,7 @@ impl GitBitbucketDriver {
     }
 
     /// @inheritDoc
-    pub fn get_change_date(&mut self, identifier: &str) -> Result<Option<DateTime<Utc>>> {
+    pub fn get_change_date(&mut self, identifier: &str) -> Result<Option<DateTime<FixedOffset>>> {
         if let Some(fallback) = self.fallback_driver.as_mut() {
             return fallback.get_change_date(identifier);
         }
@@ -486,11 +486,8 @@ impl GitBitbucketDriver {
             .fetch_with_oauth_credentials(&resource, false)?
             .decode_json()?;
 
-        // TODO(phase-b): port PHP `new \DateTimeImmutable($commit['date'])`
         let date_str = commit.get("date").and_then(|v| v.as_string()).unwrap_or("");
-        let date: DateTime<Utc> = chrono::DateTime::parse_from_rfc3339(date_str)
-            .map_err(|e| anyhow::anyhow!(e))?
-            .with_timezone(&Utc);
+        let date: DateTime<FixedOffset> = shirabe_php_shim::date_create(date_str)?;
         Ok(Some(date))
     }
 
@@ -920,7 +917,10 @@ impl crate::repository::vcs::VcsDriverInterface for GitBitbucketDriver {
         GitBitbucketDriver::get_file_content(self, file, identifier)
     }
 
-    fn get_change_date(&mut self, identifier: &str) -> anyhow::Result<Option<DateTime<Utc>>> {
+    fn get_change_date(
+        &mut self,
+        identifier: &str,
+    ) -> anyhow::Result<Option<DateTime<FixedOffset>>> {
         GitBitbucketDriver::get_change_date(self, identifier)
     }
 
diff --git a/crates/shirabe/src/repository/vcs/git_driver.rs b/crates/shirabe/src/repository/vcs/git_driver.rs
index 4878ffe..7f8c206 100644
--- a/crates/shirabe/src/repository/vcs/git_driver.rs
+++ b/crates/shirabe/src/repository/vcs/git_driver.rs
@@ -2,7 +2,7 @@
 
 use crate::io::io_interface;
 use chrono::TimeZone;
-use chrono::{DateTime, Utc};
+use chrono::{DateTime, FixedOffset, Utc};
 use indexmap::IndexMap;
 use shirabe_external_packages::composer::pcre::{CaptureKey, Preg};
 use shirabe_php_shim::{
@@ -281,7 +281,10 @@ impl GitDriver {
         Ok(Some(content))
     }
 
-    pub fn get_change_date(&mut self, identifier: &str) -> anyhow::Result<Option<DateTime<Utc>>> {
+    pub fn get_change_date(
+        &mut self,
+        identifier: &str,
+    ) -> anyhow::Result<Option<DateTime<FixedOffset>>> {
         if identifier.starts_with('-') {
             return Err(RuntimeException {
                 message: format!(
@@ -310,7 +313,9 @@ impl GitDriver {
 
         let timestamp_str = GitUtil::parse_rev_list_output(&output, &self.inner.process);
         let timestamp: i64 = timestamp_str.trim().parse().unwrap_or(0);
-        Ok(Some(Utc.timestamp_opt(timestamp, 0).unwrap()))
+        Ok(Some(
+            Utc.timestamp_opt(timestamp, 0).unwrap().fixed_offset(),
+        ))
     }
 
     pub fn get_tags(&mut self) -> anyhow::Result<IndexMap<String, String>> {
@@ -514,7 +519,10 @@ impl crate::repository::vcs::VcsDriverInterface for GitDriver {
         GitDriver::get_file_content(self, file, identifier)
     }
 
-    fn get_change_date(&mut self, identifier: &str) -> anyhow::Result<Option<DateTime<Utc>>> {
+    fn get_change_date(
+        &mut self,
+        identifier: &str,
+    ) -> anyhow::Result<Option<DateTime<FixedOffset>>> {
         GitDriver::get_change_date(self, identifier)
     }
 
diff --git a/crates/shirabe/src/repository/vcs/github_driver.rs b/crates/shirabe/src/repository/vcs/github_driver.rs
index 45ba7b7..aa1e135 100644
--- a/crates/shirabe/src/repository/vcs/github_driver.rs
+++ b/crates/shirabe/src/repository/vcs/github_driver.rs
@@ -2,13 +2,14 @@
 
 use crate::io::io_interface;
 use anyhow::Result;
-use chrono::{DateTime, Utc};
+use chrono::{DateTime, FixedOffset};
 use indexmap::IndexMap;
 use shirabe_external_packages::composer::pcre::{CaptureKey, Preg};
 use shirabe_php_shim::{
-    InvalidArgumentException, PhpMixed, RuntimeException, array_diff, array_key_exists, array_map,
-    array_search_mixed, base64_decode, basename, count, empty, explode, extension_loaded, in_array,
-    parse_url_all, sprintf, strpos, strtolower, substr, trim, urlencode,
+    DATE_RFC3339, InvalidArgumentException, PhpMixed, RuntimeException, array_diff,
+    array_key_exists, array_map, array_search_mixed, base64_decode, basename, count, empty,
+    explode, extension_loaded, in_array, parse_url_all, sprintf, strpos, strtolower, substr, trim,
+    urlencode,
 };
 
 use crate::cache::Cache;
@@ -821,7 +822,7 @@ impl GitHubDriver {
         Ok(Some(content))
     }
 
-    pub fn get_change_date(&mut self, identifier: &str) -> Result<Option<DateTime<Utc>>> {
+    pub fn get_change_date(&mut self, identifier: &str) -> Result<Option<DateTime<FixedOffset>>> {
         if let Some(ref mut git_driver) = self.git_driver {
             return git_driver.get_change_date(identifier);
         }
@@ -851,11 +852,8 @@ impl GitHubDriver {
             _ => String::new(),
         };
 
-        Ok(Some(
-            DateTime::parse_from_rfc3339(&date_str)
-                .map(|dt| dt.with_timezone(&Utc))
-                .unwrap_or_else(|_| Utc::now()),
-        ))
+        let date: DateTime<FixedOffset> = shirabe_php_shim::date_create(&date_str)?;
+        Ok(Some(date))
     }
 
     pub fn get_tags(&mut self) -> Result<IndexMap<String, String>> {
@@ -1364,7 +1362,10 @@ impl crate::repository::vcs::VcsDriverInterface for GitHubDriver {
         GitHubDriver::get_file_content(self, file, identifier)
     }
 
-    fn get_change_date(&mut self, identifier: &str) -> anyhow::Result<Option<DateTime<Utc>>> {
+    fn get_change_date(
+        &mut self,
+        identifier: &str,
+    ) -> anyhow::Result<Option<DateTime<FixedOffset>>> {
         GitHubDriver::get_change_date(self, identifier)
     }
 
diff --git a/crates/shirabe/src/repository/vcs/gitlab_driver.rs b/crates/shirabe/src/repository/vcs/gitlab_driver.rs
index 97dcc30..8ab30d4 100644
--- a/crates/shirabe/src/repository/vcs/gitlab_driver.rs
+++ b/crates/shirabe/src/repository/vcs/gitlab_driver.rs
@@ -2,13 +2,13 @@
 
 use crate::io::io_interface;
 use anyhow::Result;
-use chrono::{DateTime, Utc};
+use chrono::{DateTime, FixedOffset};
 use indexmap::IndexMap;
 use shirabe_external_packages::composer::pcre::{CaptureKey, Preg};
 use shirabe_php_shim::{
-    InvalidArgumentException, LogicException, PhpMixed, RuntimeException, array_search_mixed,
-    array_shift, ctype_alnum, empty, explode, extension_loaded, implode, in_array, is_array,
-    is_string, ord, sprintf, strpos, strtolower,
+    DATE_RFC3339, InvalidArgumentException, LogicException, PhpMixed, RuntimeException,
+    array_search_mixed, array_shift, ctype_alnum, empty, explode, extension_loaded, implode,
+    in_array, is_array, is_string, ord, sprintf, strpos, strtolower,
 };
 
 use crate::cache::Cache;
@@ -458,7 +458,7 @@ impl GitLabDriver {
         Ok(content)
     }
 
-    pub fn get_change_date(&mut self, identifier: &str) -> Result<Option<DateTime<Utc>>> {
+    pub fn get_change_date(&mut self, identifier: &str) -> Result<Option<DateTime<FixedOffset>>> {
         if let Some(ref mut git_driver) = self.git_driver {
             return git_driver.get_change_date(identifier);
         }
@@ -468,11 +468,8 @@ impl GitLabDriver {
                 .get("committed_date")
                 .and_then(|v| v.as_string())
                 .unwrap_or("");
-            return Ok(Some(
-                DateTime::parse_from_rfc3339(committed_date)
-                    .map(|dt| dt.with_timezone(&Utc))
-                    .unwrap_or_else(|_| Utc::now()),
-            ));
+            let date: DateTime<FixedOffset> = shirabe_php_shim::date_create(committed_date)?;
+            return Ok(Some(date));
         }
 
         Ok(None)
@@ -1153,7 +1150,10 @@ impl crate::repository::vcs::VcsDriverInterface for GitLabDriver {
         GitLabDriver::get_file_content(self, file, identifier)
     }
 
-    fn get_change_date(&mut self, identifier: &str) -> anyhow::Result<Option<DateTime<Utc>>> {
+    fn get_change_date(
+        &mut self,
+        identifier: &str,
+    ) -> anyhow::Result<Option<DateTime<FixedOffset>>> {
         GitLabDriver::get_change_date(self, identifier)
     }
 
diff --git a/crates/shirabe/src/repository/vcs/hg_driver.rs b/crates/shirabe/src/repository/vcs/hg_driver.rs
index c35a574..f637437 100644
--- a/crates/shirabe/src/repository/vcs/hg_driver.rs
+++ b/crates/shirabe/src/repository/vcs/hg_driver.rs
@@ -10,10 +10,10 @@ use crate::repository::vcs::VcsDriverBase;
 use crate::util::Filesystem;
 use crate::util::Hg as HgUtils;
 use crate::util::Url;
-use chrono::{DateTime, Utc};
+use chrono::{DateTime, FixedOffset, Utc};
 use indexmap::IndexMap;
 use shirabe_external_packages::composer::pcre::{CaptureKey, Preg};
-use shirabe_php_shim::{PhpMixed, RuntimeException, dirname, is_dir, is_writable};
+use shirabe_php_shim::{DATE_RFC3339, PhpMixed, RuntimeException, dirname, is_dir, is_writable};
 
 #[derive(Debug)]
 pub struct HgDriver {
@@ -197,7 +197,10 @@ impl HgDriver {
         Ok(Some(content))
     }
 
-    pub fn get_change_date(&self, identifier: &str) -> anyhow::Result<Option<DateTime<Utc>>> {
+    pub fn get_change_date(
+        &self,
+        identifier: &str,
+    ) -> anyhow::Result<Option<DateTime<FixedOffset>>> {
         if identifier.starts_with('-') {
             return Err(RuntimeException {
                 message: format!(
@@ -225,8 +228,8 @@ impl HgDriver {
             Some(self.repo_dir.clone()),
         );
 
-        let date = DateTime::parse_from_rfc3339(output.trim()).map(|d| d.with_timezone(&Utc))?;
-        Ok(Some(date))
+        let date: DateTime<Utc> = shirabe_php_shim::date_create(output.trim())?;
+        Ok(Some(date.fixed_offset()))
     }
 
     pub fn get_tags(&mut self) -> anyhow::Result<IndexMap<String, String>> {
@@ -410,7 +413,10 @@ impl crate::repository::vcs::VcsDriverInterface for HgDriver {
         HgDriver::get_file_content(self, file, identifier)
     }
 
-    fn get_change_date(&mut self, identifier: &str) -> anyhow::Result<Option<DateTime<Utc>>> {
+    fn get_change_date(
+        &mut self,
+        identifier: &str,
+    ) -> anyhow::Result<Option<DateTime<FixedOffset>>> {
         HgDriver::get_change_date(self, identifier)
     }
 
diff --git a/crates/shirabe/src/repository/vcs/perforce_driver.rs b/crates/shirabe/src/repository/vcs/perforce_driver.rs
index 0fe0f6f..65f2856 100644
--- a/crates/shirabe/src/repository/vcs/perforce_driver.rs
+++ b/crates/shirabe/src/repository/vcs/perforce_driver.rs
@@ -113,7 +113,7 @@ impl PerforceDriver {
     pub fn get_change_date(
         &self,
         _identifier: &str,
-    ) -> anyhow::Result<Option<chrono::DateTime<chrono::Utc>>> {
+    ) -> anyhow::Result<Option<chrono::DateTime<chrono::FixedOffset>>> {
         Ok(None)
     }
 
@@ -248,7 +248,7 @@ impl crate::repository::vcs::VcsDriverInterface for PerforceDriver {
     fn get_change_date(
         &mut self,
         identifier: &str,
-    ) -> anyhow::Result<Option<chrono::DateTime<chrono::Utc>>> {
+    ) -> anyhow::Result<Option<chrono::DateTime<chrono::FixedOffset>>> {
         PerforceDriver::get_change_date(self, identifier)
     }
 
diff --git a/crates/shirabe/src/repository/vcs/svn_driver.rs b/crates/shirabe/src/repository/vcs/svn_driver.rs
index ef8787a..f4e2bba 100644
--- a/crates/shirabe/src/repository/vcs/svn_driver.rs
+++ b/crates/shirabe/src/repository/vcs/svn_driver.rs
@@ -1,7 +1,7 @@
 //! ref: composer/src/Composer/Repository/Vcs/SvnDriver.php
 
 use anyhow::Result;
-use chrono::{DateTime, TimeZone, Utc};
+use chrono::{DateTime, FixedOffset, Utc};
 use indexmap::IndexMap;
 use shirabe_external_packages::composer::pcre::{CaptureKey, Preg};
 use shirabe_php_shim::{
@@ -296,7 +296,7 @@ impl SvnDriver {
         Ok(Some(output))
     }
 
-    pub fn get_change_date(&mut self, identifier: &str) -> Result<Option<DateTime<Utc>>> {
+    pub fn get_change_date(&mut self, identifier: &str) -> Result<Option<DateTime<FixedOffset>>> {
         let identifier = format!("/{}/", trim(identifier, Some("/")));
 
         let (path, rev) = if let Ok(Some(m)) =
@@ -329,10 +329,9 @@ impl SvnDriver {
                 .unwrap_or(false)
                 {
                     let date_str = m.get(&CaptureKey::ByIndex(1)).cloned().unwrap_or_default();
-                    // PHP: new \DateTimeImmutable($match[1], new \DateTimeZone('UTC'))
-                    return Ok(Utc
-                        .datetime_from_str(date_str.trim(), "%Y-%m-%d %H:%M:%S %z")
-                        .ok());
+                    return Ok(shirabe_php_shim::date_create::<Utc>(date_str.trim())
+                        .ok()
+                        .map(|d| d.fixed_offset()));
                 }
             }
         }
@@ -638,7 +637,10 @@ impl crate::repository::vcs::VcsDriverInterface for SvnDriver {
         SvnDriver::get_file_content(self, file, identifier)
     }
 
-    fn get_change_date(&mut self, identifier: &str) -> anyhow::Result<Option<DateTime<Utc>>> {
+    fn get_change_date(
+        &mut self,
+        identifier: &str,
+    ) -> anyhow::Result<Option<DateTime<FixedOffset>>> {
         SvnDriver::get_change_date(self, identifier)
     }
 
diff --git a/crates/shirabe/src/repository/vcs/vcs_driver.rs b/crates/shirabe/src/repository/vcs/vcs_driver.rs
index 94c3ff8..dc88387 100644
--- a/crates/shirabe/src/repository/vcs/vcs_driver.rs
+++ b/crates/shirabe/src/repository/vcs/vcs_driver.rs
@@ -1,9 +1,9 @@
 //! ref: composer/src/Composer/Repository/Vcs/VcsDriver.php
 
-use chrono::{DateTime, Utc};
+use chrono::{DateTime, FixedOffset};
 use indexmap::IndexMap;
 use shirabe_external_packages::composer::pcre::Preg;
-use shirabe_php_shim::{PhpMixed, extension_loaded};
+use shirabe_php_shim::{DATE_RFC3339, PhpMixed, extension_loaded};
 
 use crate::cache::Cache;
 use crate::config::Config;
@@ -94,7 +94,7 @@ impl VcsDriverBase {
     pub fn finish_base_composer_information(
         identifier: &str,
         composer_file_content: Option<String>,
-        change_date: impl FnOnce() -> anyhow::Result<Option<DateTime<Utc>>>,
+        change_date: impl FnOnce() -> anyhow::Result<Option<DateTime<FixedOffset>>>,
     ) -> anyhow::Result<Option<IndexMap<String, PhpMixed>>> {
         let content = match composer_file_content {
             None => return Ok(None),
@@ -123,7 +123,10 @@ impl VcsDriverBase {
                 .map_or(true, |v| v.as_string().map_or(true, |s| s.is_empty()))
         {
             if let Some(d) = change_date()? {
-                composer.insert("time".to_string(), PhpMixed::String(d.to_rfc3339()));
+                composer.insert(
+                    "time".to_string(),
+                    PhpMixed::String(d.format(DATE_RFC3339).to_string()),
+                );
             }
         }
 
@@ -284,7 +287,7 @@ pub trait VcsDriver: VcsDriverInterface {
             if let Some(change_date) = self.get_change_date(identifier)? {
                 composer.insert(
                     "time".to_string(),
-                    PhpMixed::String(change_date.to_rfc3339()),
+                    PhpMixed::String(change_date.format(DATE_RFC3339).to_string()),
                 );
             }
         }
diff --git a/crates/shirabe/src/repository/vcs/vcs_driver_interface.rs b/crates/shirabe/src/repository/vcs/vcs_driver_interface.rs
index e845300..5d2be04 100644
--- a/crates/shirabe/src/repository/vcs/vcs_driver_interface.rs
+++ b/crates/shirabe/src/repository/vcs/vcs_driver_interface.rs
@@ -2,7 +2,7 @@
 
 use crate::config::Config;
 use crate::io::IOInterface;
-use chrono::{DateTime, Utc};
+use chrono::{DateTime, FixedOffset};
 use indexmap::IndexMap;
 use shirabe_php_shim::PhpMixed;
 use std::cell::RefCell;
@@ -18,7 +18,10 @@ pub trait VcsDriverInterface: std::fmt::Debug {
 
     fn get_file_content(&mut self, file: &str, identifier: &str) -> anyhow::Result<Option<String>>;
 
-    fn get_change_date(&mut self, identifier: &str) -> anyhow::Result<Option<DateTime<Utc>>>;
+    fn get_change_date(
+        &mut self,
+        identifier: &str,
+    ) -> anyhow::Result<Option<DateTime<FixedOffset>>>;
 
     fn get_root_identifier(&mut self) -> anyhow::Result<String>;