Cron next run time: how to work out when a job will run

Cron expression next run time on a phone: what TickSpec shows

TickSpec: Cron Preview is an Android app for checking a five-field cron expression before you paste it somewhere else. You type or paste an expression, and the app lists up to twelve upcoming run times, starting from the next minute. That list is the cron next execution time, shown for the phone’s clock. The app does not run or schedule any job.

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  Workbench

  The Cron expression box takes the whole expression, and separate boxes for Minute, Hour, Day of month, Month and Weekday sit below it. Five preset buttons fill it in: Weekdays 9:00, Every 15 min, Daily midnight, Monthly report and Monday digest.

  The Workbench with nothing typed yet. The badge reads Check, and the app says: “Enter a five-field cron expression.”

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  Saved specs

  Give an expression a Job name and Notes, then Save spec. Each saved spec has a Load button to bring it back and a delete button. With none, the app says “No saved specs yet”.

  Three example specs in the store picture: Daily Backup, Hourly Health Check and Weekly Report, with their expressions and notes. They are sample entries.

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  Cron guide

  The in-app guide says cron runs a job “when all time fields match”, and that if both day of month and weekday are specific, TickSpec “previews either match, which is the common crontab behavior.” It lists the syntax it supports and three examples.

  The Cron guide screen with its three cards: how matching works, supported syntax, and examples.

The preview

A valid expression gets a Next run preview: numbered rows such as “Sun, Nov 15 09:00”, in 24-hour time, under the line Local zone. A Cadence map and a Field map show the schedule another way. None of the store pictures shows a valid expression with its rows, so this part is described from the app’s text and code, not from a picture.

What it accepts

Star, number, range, step, comma list, month names and weekday names. Minute 0 to 59, hour 0 to 23, day 1 to 31, month 1 to 12 or JAN to DEC, weekday 0 to 7 or SUN to SAT, with 7 read as Sunday. A reversed range is refused: “This range is reversed or outside the allowed range.” Steps must be positive whole numbers.

The day rule

The same either-one-matches rule as the POSIX text, for an expression where both day fields are filled in. A test in the project covers it.

A short summary

Under the preview, a one-line summary for a few common shapes, such as “Weekdays at 09:00.” Any other expression gets a count line, “Custom schedule with…” followed by how many minutes, hours, days, months and weekdays match. It does not translate every expression into a sentence.

What it refuses

Anything that is not exactly five fields: “Use exactly five fields separated by spaces.” That means no six-field or Quartz style expressions, and no shortcuts such as @hourly. If nothing matches within the search window, it says “No matching run time was found in the preview window.”

What it keeps

Saved job names, expressions and notes stay in the app on the phone. The privacy policy says the app has no account system or analytics, does not request the internet permission, and that saved expressions stay in local storage until you clear the app’s data or uninstall. You can delete a spec in the app. The app’s manifest also allows Android backup and its backup rules include the preferences file where saved specs are kept; the policy does not mention backup, and I did not check what Android does with it.