Paste a five-field cron expression. The reading and the next runs stay in your browser, and nothing is sent to a server.
Five fields: minute, hour, day of month, month, day of week. Names like MON and JAN work.
A cron expression is five fields: minute, hour, day of month, month, and day of week. The classic table is the one documented in crontab(5). Minute runs from 0 to 59, hour from 0 to 23, day of month from 1 to 31, month from 1 to 12, and day of week from 0 to 7.
A star means every value of that field. A list uses commas, a range uses a hyphen, and a step uses a slash. Month names JAN to DEC and day names SUN to SAT are the three-letter forms from crontab(5). Both 0 and 7 mean Sunday.
0 9 * * 1-5
At minute 0 At hour 9 Every day of the month Every month On Monday, Tuesday, Wednesday, Thursday, Friday
*/15 * * * *
At minute 0, 15, 30, 45 Every hour Every day of the month Every month Every day of the week
0 0 9 * * 1-5
0 9 * * 1-5
When the day of month and the day of week are both restricted, crontab(5) runs the command if either field matches. A star is the only unrestricted form. 1-31 still counts as restricted. This page follows that rule, and it says so under the reading.
An unreadable expression keeps the previous reading. Day 31 never falls in February, so an expression that only asks for 31 February reports no run in the next 366 days.
Cron itself has no time zone. The next runs use the local time zone of the browser, at a resolution of one minute. The current minute is included only when the clock is exactly on second 0.
The share link stores the expression. The reading and the next runs are computed again when the link is opened, so the runs move forward with the clock.
The name cron comes from the Greek χρόνος (chrónos), time. The five-field table used here is the one in the Vixie cron manual page, crontab(5).
Sunday is 0, and it is also 7, so a week can be written 0-6 or 1-7. MON is 1 and SUN is 0. Names are matched in either letter case, and only the three-letter form is accepted.