Unix Time Guide: Epoch Basics, Precision, and Best Practices

Unix time (a.k.a. epoch time) counts seconds since 1970‑01‑01 00:00:00 UTC. It’s universal, compact, and fast to compare.

Why it’s useful

• Same moment globally, no timezone ambiguity (store in UTC)
• Numeric comparisons are trivial
• Small footprint compared to strings

Precisions

• Seconds (classic 32/64-bit integer)
• Milliseconds (JavaScript’s Date.now())
• Microseconds and Nanoseconds (databases, tracing)

Conversions

• To human‑readable: multiply by 1000 to get milliseconds when building a JS Date
• From date/time: convert chosen unit carefully (avoid mixing s and ms)

Time Zones

Store in UTC. Convert for display with locales/time zones. Our Timezone Converter shows multi‑region views.

Y2K38

32‑bit signed time_t overflows at 2038‑01‑19 03:14:07 UTC. Use 64‑bit ints and validate ranges.

Best Practices

1. Standardize on one precision in your system
2. Store UTC; localize at the edges (UI)
3. Validate inputs and document expectations
4. Keep conversions pure and tested

Need to try things out? Head back to the converter or the batch tool.