[php-src] Issue #8275: Function strtotime("-x month", ...) returns different month if the date part is 01-28 or >=29. Additionally different
behaviour for leap and non-leap years

Issue: https://github.com/php/php-src/issues/8275 Comment Author: alex-kalanis Do not rely on ``strtotime()` function too much. It depends on system timezones. Use [`\DateTime`](https://www.php.net/manual/en/class.datetime.php) class and its methods and other classess and interfaces. For adding and subtracting use especially [`\DateInterval``](https://www.php.net/manual/en/class.dateinterval.php). For this problem use another way - calculate amount of days in Feburary. Because exceptions in leap year where every 100th (2100, 2200) is NOT leap BUT every 400th is (2000, 2400). ```php <?php function date_function_check($year, $month, $isleapyear, $timezone = null) { $date = \DateTime::createFromFormat('Y-m-d', sprintf('%04d-%02d-%02d', $year, 2, 1), $timezone); $nextMonth = clone $date; $nextMonth->add(new \DateInterval('P1M')); $interval = $date->diff($nextMonth); $status = ''; if ($interval->days < 29) { $status = 'not'; } echo sprintf('The year %04d is %s leap %s', $year, $status, PHP_EOL); } ``` This example code may need a bit debug, I wrote it just as proof-of-concept.