Build and validate cron expressions with a visual editor showing human-readable schedule descriptions.
Write a cron schedule without memorizing the five-field format. The tool splits an expression into its fields - minute, hour, day of month, month, day of week - lets you set each one through a visual editor, assembles the standard crontab string, and renders a plain-language description of when the job will fire, so the schedule is validated before it reaches a server. The thing people most often get wrong: when both day-of-month and day-of-week are restricted, standard cron runs the job when either matches, not when both do. `0 0 1 * MON` fires on the 1st of every month AND on every Monday.
A concrete input and expected output from the current implementation.
Input
0 0 1 * MON
Expected output
At 12:00 AM, on day 1 of the month, and on Monday
Day-of-month (1) and day-of-week (MON) are both restricted, so standard cron treats them as alternatives: the job fires at midnight on the 1st of each month and also at midnight every Monday - about 4 to 6 runs per month, not one.
Each of the five standard fields is edited separately: a fixed value, a list like 1,15, a range like 9-17, or a step like */15. The tool assembles the pieces in the fixed cron order - minute, hour, day of month, month, day of week - so the generated string is always structurally valid. Names such as MON and JAN work alongside numeric values.
Values are checked against each field's allowed range - minutes 0-59, hours 0-23, days 1-31, months 1-12, weekdays 0-7 where 0 and 7 both mean Sunday - and out-of-range input is flagged. The readable description is produced by expanding the expression field by field: ranges are inclusive, steps list every matching value, and a restricted day-of-month combined with a restricted day-of-week renders as an either/or.
Because standard cron treats the two day fields as alternatives. With both restricted, the job runs at the set time on the 1st of each month and again on every Monday - about 4 to 6 times a month. A single standard expression cannot express 'only when both match'; add a weekday check inside the command itself.
Standard cron has no seconds or year fields, so a five-field expression is all the common crontab accepts. If the target scheduler runs Quartz or Spring, which read seconds first and an optional year, check whether this tool offers that dialect before trusting the string - otherwise paste it into a Quartz-specific editor.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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