ISO 8601 vs Unix timestamps: which date format should your API use?
ISO 8601 dates (like 2026-06-03T14:30:00Z) are human-readable, self-describing, and sortable as strings. Unix timestamps (like 1748965800) are compact integers that are timezone-independent and trivial to do math on. Choosing between them for your API or database is a trade-off between developer experience and machine efficiency.
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Unix Timestamp Converter
Convert between Unix timestamps and human-readable dates.
# Timestamp to Date
📅 Date to Timestamp
How this is calculated
ISO 8601 wins on developer experience. Anyone reading a log file or API response can instantly understand the date without a converter. It's the standard for JSON APIs (JSON doesn't have a native date type), and it's what JavaScript's Date.toISOString() produces. Unix timestamps win on compactness (10 digits vs 24 characters) and math (subtracting two timestamps gives you a duration in seconds with no parsing). Databases handle both well. PostgreSQL has native timestamp types. SQLite stores everything as strings anyway.
Verdict
Use ISO 8601 strings for public APIs and anywhere a human might read the raw data. Use Unix timestamps for internal services, high-volume event streams, and anywhere you need to do date math. You can have both: store as Unix timestamp in the database, serialize as ISO 8601 at the API boundary.
Frequently asked questions
Is ISO 8601 always in UTC?
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