Unix 时间戳指南

What a timestamp is

A Unix timestamp is the number of seconds or milliseconds elapsed since 1970-01-01 00:00:00 UTC (the epoch) — a pure-numeric absolute instant:

0            → 1970-01-01 00:00:00 UTC
1780000000   → some second around 2026-05-29 (seconds)
1780000000000 → the same instant (milliseconds)

It depends on no time zone and no language format — which is why logs, databases, and APIs all use it.

10-digit seconds vs 13-digit ms

Conversion is ×1000 / ÷1000. Our Timestamp tool auto-detects by digit count with a manual override.

Time zone traps

• Timestamps have no time zone: they're absolute durations; only rendering as "2026-09-27 14:00" involves a zone
• An 8-hour offset isn't a bug: it's the fixed UTC vs Beijing (UTC+8) difference
• Always pass timestamps, never date strings: "09/27/2026" means different dates in different regions; timestamps are unambiguous
• Store UTC in databases: localize at the display layer — mixing the two is the #1 source of time zone bugs

Writing ISO 8601

2026-09-27T14:00:00Z            (Z = UTC, most standard)
2026-09-27T14:00:00+08:00       (with an offset)
2026-09-27T14:00:00             ⚠ no zone — parsers guess, don't do this

Rule: ISO 8601 (with zone) for humans, timestamps for machines.

Per-language snippets

// JavaScript (ms)
Date.now()                        // current ms
new Date(1780000000000)           // ms → Date
Math.floor(ts / 1000)             // ms → s

# Python (s, float)
import time; time.time()          // current s
from datetime import datetime, timezone
datetime.fromtimestamp(1780000000, tz=timezone.utc)

// Java (ms)
System.currentTimeMillis();
Instant.ofEpochSecond(1780000000L);   // seconds

// Go (s, ns)
time.Now().Unix()                 // seconds
time.Now().UnixMilli()            // milliseconds

-- SQL (MySQL)
UNIX_TIMESTAMP()                  -- current s
FROM_UNIXTIME(1780000000)         -- s → datetime

FAQ