Tools
Cron Expression Builder
WORKINGType a 5-field cron expression, get a plain-English explanation and the next five run times in your local clock.
minute · hour · day-of-month · month · day-of-week
Next runs (your local time)
The one non-obvious rule cron itself gets right and most explainers skip: when both day-of-month and day-of-week are restricted, a day matching either one counts — it’s an OR, not an AND. 0 0 15 * 1 doesn’t mean “the 15th, if it’s a Monday” — it fires on the 15th of every month and every Monday.
The plain-English description is template-matched against the common shapes (every N minutes, a daily time, a weekday range, a day-of-month); anything odd enough to fall outside those templates still gets the literal resolved field values instead of a guessed-at sentence.
- Built
- Category
- utility
- Stack
- JavaScript
- Details
- Each field parses into a Set of matching integers (handling *, */n, ranges and a-b/n steps), then next-run search walks forward minute-by-minute against those sets, capped at ~4 years so a self-contradictory expression (Feb 30) terminates instead of looping forever.
- Model
- Claude Sonnet 5
- Source
- View source →