fix(I18n): compute correct date in Time::today(), yesterday(), and tomorrow() across timezones (#10532)

* fix(I18n): fix timezone and testNow calculation in Time::today(), yesterday(), and tomorrow()

- Compute start of day relative to the requested timezone instead of the server default timezone
- Respect Time::setTestNow() mock instance in today(), yesterday(), and tomorrow()
- Add unit tests covering date boundary transitions across different timezones
- Add changelog entry in v4.7.5.rst

* Update user_guide_src/source/changelogs/v4.7.5.rst

Co-authored-by: neznaika0 <ozornick.ks@gmail.com>

* Fix multiple bugs in Files, Helpers, Honeypot, I18n, Logger, and Cache

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* fix(I18n): address review suggestions for Time::today/yesterday/tomorrow

Use new static(null) instead of static::now() to avoid coupling overridable extension points, and freeze time in testTodayLocalized to prevent intermittent failure across timezones.

* Update system/I18n/TimeTrait.php

Co-authored-by: Michal Sniatala <michal@sniatala.pl>

* Update tests/system/I18n/TimeTest.php

Co-authored-by: Michal Sniatala <michal@sniatala.pl>

* Update system/I18n/TimeTrait.php

Co-authored-by: Michal Sniatala <michal@sniatala.pl>

* Update tests/system/I18n/TimeTest.php

Co-authored-by: Michal Sniatala <michal@sniatala.pl>

* style: correct indentation in TimeTest

---------

Co-authored-by: neznaika0 <ozornick.ks@gmail.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Michal Sniatala <michal@sniatala.pl>

Author: 4 people

system/I18n/TimeTrait.php

@@ -144,7 +144,7 @@ public static function parse(string $datetime, $timezone = null, ?string $locale
      */
     public static function today($timezone = null, ?string $locale = null)
     {
-        return new static(date('Y-m-d 00:00:00'), $timezone, $locale);
+        return (new static(null, $timezone, $locale))->setTime(0, 0, 0, 0);
     }
 
     /**
@@ -158,7 +158,7 @@ public static function today($timezone = null, ?string $locale = null)
      */
     public static function yesterday($timezone = null, ?string $locale = null)
     {
-        return new static(date('Y-m-d 00:00:00', strtotime('-1 day')), $timezone, $locale);
+        return (new static(null, $timezone, $locale))->modify('yesterday');
     }
 
     /**
@@ -172,7 +172,7 @@ public static function yesterday($timezone = null, ?string $locale = null)
      */
     public static function tomorrow($timezone = null, ?string $locale = null)
     {
-        return new static(date('Y-m-d 00:00:00', strtotime('+1 day')), $timezone, $locale);
+        return (new static(null, $timezone, $locale))->modify('tomorrow');
     }
 
     /**

tests/system/I18n/TimeLegacyTest.php

@@ -170,9 +170,14 @@ public function testToday(): void
 
     public function testTodayLocalized(): void
     {
+        // Freeze time to avoid flakiness when server and London are on different calendar days
+        TimeLegacy::setTestNow('2026-06-15 12:00:00', 'UTC');
+
         $time = TimeLegacy::today('Europe/London');
 
-        $this->assertSame(date('Y-m-d 00:00:00'), $time->toDateTimeString());
+        $this->assertSame('2026-06-15 00:00:00', $time->toDateTimeString());
+
+        TimeLegacy::setTestNow();
     }
 
     public function testYesterday(): void

tests/system/I18n/TimeTest.php

@@ -171,9 +171,14 @@ public function testToday(): void
 
     public function testTodayLocalized(): void
     {
+        // Freeze time to avoid flakiness when server and London are on different calendar days
+        Time::setTestNow('2026-06-15 12:00:00', 'UTC');
+
         $time = Time::today('Europe/London');
 
-        $this->assertSame(date('Y-m-d 00:00:00'), $time->toDateTimeString());
+        $this->assertSame('2026-06-15 00:00:00', $time->toDateTimeString());
+
+        Time::setTestNow();
     }
 
     public function testYesterday(): void
@@ -190,6 +195,65 @@ public function testTomorrow(): void
         $this->assertSame(date('Y-m-d 00:00:00', strtotime('+1 day')), $time->toDateTimeString());
     }
 
+    public function testTodayWithTimezoneAcrossDateBoundary(): void
+    {
+        // When UTC is 2026-09-07 23:30:00, in Asia/Tokyo (+09:00) it is already 2026-09-08 08:30:00
+        Time::setTestNow('2026-09-07 23:30:00', 'UTC');
+
+        $tokyoToday = Time::today('Asia/Tokyo');
+        $this->assertSame('2026-09-08 00:00:00', $tokyoToday->toDateTimeString());
+
+        // When UTC is 2026-09-08 02:00:00, in America/New_York (-04:00 EDT) it is still 2026-09-07 22:00:00
+        Time::setTestNow('2026-09-08 02:00:00', 'UTC');
+
+        $nyToday = Time::today('America/New_York');
+        $this->assertSame('2026-09-07 00:00:00', $nyToday->toDateTimeString());
+
+        Time::setTestNow();
+    }
+
+    public function testYesterdayWithTimezoneAcrossDateBoundary(): void
+    {
+        // When UTC is 2026-09-07 23:30:00, in Tokyo it is 2026-09-08, so Tokyo yesterday is 2026-09-07
+        Time::setTestNow('2026-09-07 23:30:00', 'UTC');
+
+        $tokyoYesterday = Time::yesterday('Asia/Tokyo');
+        $this->assertSame('2026-09-07 00:00:00', $tokyoYesterday->toDateTimeString());
+
+        // When UTC is 2026-09-08 02:00:00, in NY it is 2026-09-07, so NY yesterday is 2026-09-06
+        Time::setTestNow('2026-09-08 02:00:00', 'UTC');
+
+        $nyYesterday = Time::yesterday('America/New_York');
+        $this->assertSame('2026-09-06 00:00:00', $nyYesterday->toDateTimeString());
+        // March 28 at 23:30 does not exist in Nuuk due to the DST transition.
+        Time::setTestNow('2026-03-29 23:30:00', 'America/Nuuk');
+
+        $nuukYesterday = Time::yesterday('America/Nuuk');
+        $this->assertSame('2026-03-28 00:00:00', $nuukYesterday->toDateTimeString());
+        Time::setTestNow();
+    }
+
+    public function testTomorrowWithTimezoneAcrossDateBoundary(): void
+    {
+        // When UTC is 2026-09-07 23:30:00, in Tokyo it is 2026-09-08, so Tokyo tomorrow is 2026-09-09
+        Time::setTestNow('2026-09-07 23:30:00', 'UTC');
+
+        $tokyoTomorrow = Time::tomorrow('Asia/Tokyo');
+        $this->assertSame('2026-09-09 00:00:00', $tokyoTomorrow->toDateTimeString());
+
+        // When UTC is 2026-09-08 02:00:00, in NY it is 2026-09-07, so NY tomorrow is 2026-09-08
+        Time::setTestNow('2026-09-08 02:00:00', 'UTC');
+
+        $nyTomorrow = Time::tomorrow('America/New_York');
+        $this->assertSame('2026-09-08 00:00:00', $nyTomorrow->toDateTimeString());
+        // Moving forward must select March 28 without normalizing into March 29.
+        Time::setTestNow('2026-03-27 23:30:00', 'America/Nuuk');
+
+        $nuukTomorrow = Time::tomorrow('America/Nuuk');
+        $this->assertSame('2026-03-28 00:00:00', $nuukTomorrow->toDateTimeString());
+        Time::setTestNow();
+    }
+
     public function testCreateFromDate(): void
     {
         $time = Time::createFromDate(2017, 03, 05, 'America/Chicago');

user_guide_src/source/changelogs/v4.7.5.rst

@@ -50,6 +50,7 @@ Bugs Fixed
 - **Files:** Fixed a bug where ``File::move()`` and ``UploadedFile::move()`` set executable and overly permissive file permissions (``0777 & ~umask()`` instead of ``0666 & ~umask()``), and ``UploadedFile::move()`` targeted the parent directory instead of the destination file for ``chmod()``.
 - **Helpers:** Fixed a bug where ``get_dir_file_info()`` returned incomplete entries for subdirectories and missing files instead of omitting them.
 - **Honeypot:** Fixed a bug where bot detection returned an HTTP 500 response instead of 403 (Forbidden).
+- **I18n:** Fixed a bug where ``Time::today()``, ``Time::yesterday()``, and ``Time::tomorrow()`` ignored the specified ``$timezone`` and ``setTestNow()`` when calculating the day.
 - **Logger:** Fixed a bug where interpolating a log message with array or non-stringable context values could raise PHP warnings or errors.
 - **Cache:** Fixed ``MemcachedHandler::decrement()`` initializing a non-existent counter to the positive offset. Missing counters are now initialized to ``0``, reflecting Memcached's unsigned, saturating counter semantics.