Developer Tools
Cron, timestamps, regex and bandwidth converters for developers.
Cron Expression Builder & Translator
Build cron expressions visually and translate any cron string to plain English with the next 5 fire times.
Unix Timestamp Converter (with Timezone)
Bidirectional Unix timestamp ↔ human date converter with timezones, milliseconds and ISO 8601.
Bandwidth & Download Time Calculator (Mbps ↔ MB/s)
Convert Mbps to MB/s and calculate download time for any file size at any internet speed.
Regex Tester with Plain English Explainer
Test regular expressions live with match highlighting and a plain English breakdown of every part of the pattern.
What these tools are for
These are the conversions that are quick to do wrong in your head and slow to debug afterwards. Cron expressions are the worst offender: the five fields are minute, hour, day-of-month, month, day-of-week, and the day-of-month and day-of-week fields are ORed rather than ANDed when both are restricted — which is why a schedule intended for "the first Monday" fires far more often than expected.
Timestamps have their own traps. Unix time is seconds since the epoch in UTC with no leap seconds, milliseconds versus seconds is a factor-of-1000 error that still parses cleanly, and anything involving a local time zone needs the zone recorded alongside it or the value is ambiguous twice a year.
Bandwidth conversions trip on bits versus bytes and on the decimal-versus-binary prefix split. A "100 Mb" line moves 12.5 MB per second at best, and drive manufacturers count a gigabyte as 10⁹ bytes while your operating system may not.
Which one do I want?
- Writing or reading a cron schedule
- Cron builder — it explains the expression in words.
- Converting an epoch value
- Unix timestamp.
- Working out transfer time
- Bandwidth converter — mind bits versus bytes.