plain-English explainers for working with time in software

Guides.

Timestamps look simple until they aren’t. These guides cover the questions that come up again and again when you’re reading logs, writing code or wrangling data — with worked examples you can check in the converter.

• What is Unix time?

  What a Unix timestamp actually counts, why it starts on 1 January 1970, how leap seconds and negative values work, and why developers use it everywhere.

• Seconds vs milliseconds vs nanoseconds

  Identify the unit of any epoch timestamp by its number of digits, see which languages and systems use which unit, and avoid the classic off-by-1000 bug.

• The Year 2038 problem

  Why 32-bit Unix timestamps overflow at 03:14:07 UTC on 19 January 2038, which systems are still at risk, and how 64-bit time fixes it.

• Unix timestamps in every language

  Copy-paste snippets to get the current Unix timestamp and convert it back to a date in JavaScript, Python, Java, Go, C#, PHP, Ruby, Rust, Bash, PostgreSQL, MySQL and SQLite.

• UTC, ISO 8601 & time zones

  How Unix timestamps relate to UTC and local time, how to read ISO 8601 and RFC 3339 strings, and practical rules for handling time zones and daylight saving time.

• Timestamps in Excel & Google Sheets

  Formulas to convert Unix epoch timestamps to readable dates in Excel and Google Sheets and back again, including milliseconds and time zone adjustments.