How to generate a timestamp with an absolute template

// Examples assume a current time of Thursday, 12/18/2025 10:12
$date1 = strtotime('2020-09-11'); // 1599796800 09/11/2020
$date2 = strtotime('9/11/2020'); // 1599796800 09/11/2020
$date3 = strtotime('Sep 11'); // 1757563200 09/11/2025
$date4 = strtotime('8:45 am'); // 1766065500 08:12 am
$date5 = strtotime('8am'); // 1766062800 08 am
$date6 = strtotime('2020-09-11 8:45 am'); // 1599828300 09/11/2020 08:09 am

How to generate a timestamp with a relative template

// Examples assume a current time of Thursday, 12/18/2025 10:12
$date1 = strtotime('+1 hour'); // 11:51 am
$date2 = strtotime('-2 days'); // 12/16/2025
$date3 = strtotime('tomorrow'); // 12/19/2025
$date4 = strtotime('tomorrow 10:15am'); // 12/19/2025 10:15 am
$date5 = strtotime('next sunday'); // 12/21/2025
$date6 = strtotime('last day of'); // 12/31/2025
$date7 = sttotime('first day of next month'); // 01/01/2026
$date8 = strtotime('third wednesday of'); // 12/17/2025
$date9 = strtotime('nov second thu of 8am'); // 11/13/2025 08:00 am

How to modify a timestamp

$checkout = mktime(13, 30, 0, 9, 8, 2017); // 1766076689 12/18/2025 11:12 am
$due_date = strtotime('+3 weeks 6pm', $checkout); // 1767913200 01/08/2026 06:01 pm

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