Unix Timestamps and Epoch Time: The Developer's Complete Guide

What Is a Unix Timestamp?

A Unix timestamp (also called epoch time or POSIX time) is the number of seconds that have elapsed since January 1, 1970, 00:00:00 UTC. That moment — the "Unix epoch" — is the zero point of Unix time.

Right now, the Unix timestamp is approximately 1,781,000,000 (it increases by 1 every second).

Why Developers Use Timestamps

Timestamps solve the hardest problem in programming: time.

• No timezone ambiguity — 1700000000 means the same moment everywhere on Earth
• Easy math — "30 minutes ago" is just now - 1800
• Database-friendly — integers sort and index faster than datetime strings
• Language-agnostic — every language can work with a number

Seconds vs. Milliseconds

This is the #1 source of timestamp bugs:

• Unix timestamps are in seconds (10 digits): 1700000000
• JavaScript `Date.now()` returns milliseconds (13 digits): 1700000000000
• Java `System.currentTimeMillis()` also returns milliseconds

If your timestamp has 13 digits, divide by 1000 to get seconds. If you mix them up, your dates will be in the year 55,000.

Common Timezone Pitfalls

1. Storing Local Time Instead of UTC

Never store a timestamp derived from local time without converting to UTC first. "2024-01-15 12:00:00" means different moments in New York vs. Tokyo.

2. Daylight Saving Time

DST creates hours that don't exist (spring forward) and hours that happen twice (fall back). Always use UTC internally and convert to local time only for display.

3. The 2038 Problem

A 32-bit signed integer overflows on January 19, 2038 at 03:14:07 UTC. After that, 32-bit Unix timestamps wrap to negative numbers (interpreted as 1901). Most modern systems use 64-bit timestamps, but legacy systems and embedded devices may still be vulnerable.

Quick Conversions

Try It Now

Need to convert a timestamp right now? Use our [free epoch converter](/tools/epoch-converter). It shows the current Unix timestamp live, converts both directions (timestamp ↔ date), and auto-detects seconds vs. milliseconds.

Timestamps in Error Tracking

When debugging production errors, accurate timestamps are critical. Was the error before or after that deploy? Did the timeout happen during a traffic spike?

Bugsly captures precise timestamps for every error event and breadcrumb, and displays them in both UTC and your local timezone. [Start tracking errors](/signup) with timestamps you can trust.