Cron Expression Builder — Visual Cron Generator & Scheduler

You need to schedule a job to run every weekday at 9 AM, or every 15 minutes during business hours, or on the 1st and 15th of every month — but cron syntax is easy to get wrong. A misplaced * or an off-by-one in a range can silently cause a job to fire too often, too rarely, or never at all. Use this visual builder to construct the expression by clicking, then verify the next 6 run times before the expression touches production.

The builder breaks each of the five fields (minute hour day-of-month month day-of-week) into a dedicated panel. Instead of remembering whether Monday is 1 or 0, you click "Monday" and the tool writes the correct value. Choose Every to use *, Every N for step notation like */5, Range for a 1-5 span, or Specific to pick individual values from a named grid. The expression at the top updates in real time — power users can also type directly into the expression input and the builder panels will sync.

The human-readable description converts any valid expression to plain English: "Every 15 minutes", "At 9:00 AM, Monday through Friday", "First day of every quarter at midnight". It first checks the expression against a lookup table of common canonical forms for an exact, hand-written phrase, and only falls back to a rule-based sentence builder — one clause per field — for anything less common, which is why the frequent presets read especially naturally while rarer combinations still get a correct, if plainer, description.

The Next Run Times panel doesn't solve for run times mathematically — it walks forward minute by minute from now, checking each candidate against all five parsed fields, but jumps ahead intelligently when a whole unit fails to match: a non-matching month skips straight to the 1st of the next month, a non-matching day jumps to midnight the next day, and so on, rather than stepping one minute at a time through months that can never match. That walk is capped at roughly 700,000 iterations — about a year and a half of minutes — so an expression that only fires on February 29th, or another rare combination, resolves to an explicit warning instead of hanging the browser. When both the day-of-month and day-of-week fields are restricted at the same time, the calculator follows the same OR-logic convention as standard Vixie cron: a day counts as a match if *either* field's condition is satisfied, not only when both are — the same field-7-means-Sunday normalization is applied too, since some cron dialects use 7 as an alternate for Sunday alongside 0. Catches off-by-one errors before they reach production. Supports @hourly, @daily, @weekly, @monthly, and @yearly aliases, plus 16 common presets for instant loading. All calculations run in your browser — no data is sent to any server.