What Is a Unix Timestamp?

A Unix timestamp (also called Unix time or epoch time) counts how much time has passed since a fixed starting point called the Unix epoch:

1970-01-01 00:00:00 UTC

That instant is defined as 0. Every moment after it gets a positive integer; moments before 1970 get negative values.

Why integers instead of strings?

Storing time as a number has practical advantages:

• Sorting chronological events is trivial (ORDER BY created_at)
• Arithmetic is easy (duration = end − start)
• Timezone-neutral at storage — the integer names one instant on the global timeline; display layers choose UTC or local formatting

Strings like "2024-06-01T12:00:00" are human-friendly but ambiguous unless you also store offset or timezone rules.

Where you see Unix timestamps

Common places:

• Server logs — often seconds since epoch in one field
• JWT iat / exp claims — usually seconds
• JavaScript — Date.now() returns milliseconds
• PostgreSQL — EXTRACT(EPOCH FROM ...) returns seconds with fractional part
• Mobile analytics — mixed; always check docs

Not the same as “local clock reading”

1700000000 does not mean “5 PM in my city” by itself. It names a single instant; your UI converts that instant to local wall time for display.

Key takeaway

Unix timestamps are portable counters of time since 1970-01-01 UTC. Learn the epoch once and logs, tokens, databases, and API fields become much easier to decode.