[wp-trac] [WordPress Trac] #63772: get_calendar() shows incorrect month-end due to current_time() timezone issue

[WordPress Trac]

#63772: get_calendar() shows incorrect month-end due to current_time() timezone
issue
--------------------------+-----------------------------
 Reporter:  smilkobutawp  |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Date/Time     |    Version:  6.8.2
 Severity:  normal        |   Keywords:  needs-patch
  Focuses:                |
--------------------------+-----------------------------
 The get_calendar() function in WordPress incorrectly calculates the number
 of days in the current month when the site timezone is set to UTC+9 (e.g.,
 Asia/Tokyo) and the current time is near the end of the month (e.g., July
 31st around 22:00–23:59 JST).
 🔁 Steps to Reproduce:

 1. Set your WordPress site timezone to Asia/Tokyo (UTC+9).

 2. Visit a page that displays the default calendar widget.

 3. On July 31, 2025, at 22:37 JST, observe that the calendar for July only
 shows up to the 30th, even though July has 31 days.

 4. Inspect wp-includes/general-template.php, where get_calendar() uses the
 following:

 $thisyear  = (int) current_time( 'Y' );
 $thismonth = (int) current_time( 'm' );
 $unixmonth = mktime( 0, 0, 0, $thismonth, 1, $thisyear );
 $last_day  = gmdate( 't', $unixmonth );

 This calculation yields an incorrect $thismonth = 8 (August), causing
 $last_day = 30 instead of 31 for July.
 🧠 Technical Cause:

 current_time('Y') and current_time('m') are localized string values, but
 they are influenced by UTC time logic internally, especially near the date
 change boundary. As a result, the calendar may "roll over" to the next
 month prematurely.
 ✅ Suggested Fix:

 Use current_time('timestamp') or better yet, rely on the correct timezone-
 aware approach using wp_timezone():

 $dt = new DateTimeImmutable( 'now', wp_timezone() );
 $thisyear = (int) $dt->format( 'Y' );
 $thismonth = (int) $dt->format( 'm' );
 $unixmonth = $dt->setDate( $thisyear, $thismonth, 1 )->getTimestamp();
 $last_day = gmdate( 't', $unixmonth );

 ✅ Confirmed Result:

 On 2025-07-31 22:37 JST, this code correctly yields:

 $thisyear = 2025
 $thismonth = 7
 $last_day = 31

 This provides accurate calendar generation behavior, aligned with local
 timezone settings.

 Please consider updating get_calendar() to use timezone-aware logic in
 future versions to prevent subtle bugs in calendar rendering for
 international users.

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Ticket URL: <https://core.trac.wordpress.org/ticket/63772>
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