Cron for Every 90 Minutes

Cron's minute field only covers 0–59, so a single line can't step forward by 90 minutes and carry the remainder into the hour field. The clean way to get an exact 90-minute cadence is two cron lines together, alternating between the top and half of alternating hours:

0 0,3,6,9,12,15,18,21 * * * (runs at :00 on every 3rd hour) plus 30 1,4,7,10,13,16,19,22 * * * (runs at :30 on the hours in between). Together they fire at 00:00, 01:30, 03:00, 04:30, 06:00 — an unbroken 90-minute interval around the clock, every day.

Want to build a different schedule, or check how a related expression behaves? Open this exact expression in the full Cron Expression Builder to edit it directly.