# IndieCrontab > See what a cron expression means, its next five runs, and whether Cloudflare, GitHub Actions, Vercel, and AWS accept it. One cron, one sourced answer. Free, no account. The canonical page is https://indiecrontab.com/. ## Use the tool Open [IndieCrontab](https://indiecrontab.com/) to complete the job. The questions below describe the supported input, result, and limits. Every answer names its source next to it. Source: [crontab(5), Linux manual](https://man7.org/linux/man-pages/man5/crontab.5.html). ## Questions and limits ### What is a cron expression? A cron expression is a five-field schedule: minute, hour, day of month, month, and day of week, separated by spaces. `*` means every value, a list such as `1,15` names values, a range such as `9-17` spans them, and a step such as `*/15` repeats. The rules come from the Unix [crontab(5)](https://man7.org/linux/man-pages/man5/crontab.5.html) manual. IndieCrontab reads the expression, writes out what it means in plain words, and lists its next five runs. ### What timezone does cron run in? It depends on the scheduler. Cloudflare Cron Triggers and Vercel Cron Jobs always evaluate the expression in UTC. GitHub Actions and AWS EventBridge Scheduler use UTC unless a timezone is configured there. A cron daemon on your own server uses that machine's zone. IndieCrontab evaluates every expression in UTC and shows the five runs in your browser's zone, or any zone you pick, with the offset at each run. The picker changes how a run reads, never when it happens. When a clock change falls between two runs, the page says so. ### Does 0 or 7 mean Sunday in cron? In crontab(5), both do: the day of week field runs from 0 to 7, and 0 and 7 are both Sunday. The platforms disagree. GitHub Actions and Vercel document 0 through 6, so 7 is out of range there. Cloudflare numbers the week from 1 for Sunday through 7 for Saturday, so `0` is invalid and `1-5` means Sunday through Thursday. The three-letter names `SUN` through `SAT` keep one meaning everywhere except Vercel, which accepts numbers only. IndieCrontab names the problem in the platform row. ### Why does Vercel or GitHub Actions reject my cron expression? Each platform accepts a subset of crontab. [Vercel](https://vercel.com/docs/cron-jobs) refuses month and weekday names, weekday 7, and an expression that sets both day of month and day of week, and its Hobby plan runs a job once a day at an hour it picks within. GitHub Actions refuses weekday 7 and any schedule that runs more often than once every five minutes. Cloudflare accepts five fields in UTC but numbers weekdays from 1 for Sunday, so a numeric weekday reads differently there. AWS EventBridge Scheduler wants `cron(...)` with a sixth year field, so every five-field expression needs a rewrite there. Every platform row names the rule it applied and links to the vendor page it rests on. ### Which cron syntax does the check not support? IndieCrontab reads the common five-field form: `*`, lists, inclusive ranges, steps, and three-letter month and weekday names. It does not read nicknames such as `@daily` or `@hourly`, a sixth seconds or year field, or the Quartz and AWS extensions `L`, `W`, `#`, and `?`. Rewrite those into five fields first. The platform rules were read from each vendor's own documentation on the date shown under the result. Plan limits and vendor rules change, so treat a row as a pointer to that page rather than a promise. The next runs are searched 80 years ahead at most, so an expression naming a date that never comes, such as day 31 of February, is refused. ## Promises - The core is free: no account, no card, no premium plan, no upgrade nag, no hidden paywall. - Private lookup activity is never published. - Analytics is currently off. Private lookup activity is never published or sent to a tracker. No lookup history becomes public inventory. ## More - [Notes](https://indiecrontab.com/blog.md): posts by the maker, newest first - [More tools](https://indiecrontab.com/tools.md): the other tools by turushan - [security.txt](https://indiecrontab.com/.well-known/security.txt): how to report a vulnerability Made by turushan, https://twitter.com/turushan.