Timestamp Converter

Purpose

Online Unix timestamp converter supporting both seconds (10 digits) and milliseconds (13 digits) with bidirectional conversion to readable date/time. Recognizes local timezone and UTC switching, supports ISO 8601, RFC 2822, and custom output formats. Live current-timestamp display with one-click copy. Common in backend log triage, API time field debugging, database created_at field cross-check, scheduled task time verification, and cross-timezone meeting time calculation. All conversion happens locally.

Steps

1. Input 10-digit (seconds) or 13-digit (milliseconds) timestamp on the left; auto-detected
2. Right pane shows readable date/time in both local timezone and UTC simultaneously
3. Reverse: pick a date and time, get corresponding timestamp (both seconds and milliseconds)
4. Timezone switching: local, UTC, Asia/Tokyo, America/New_York, etc.
5. Current timestamp: live-updating seconds and milliseconds with copy button
6. ISO 8601 format: 2026-01-01T08:00:00.000Z (API standard format)
7. Relative time: "3 hours ago" / "5 days from now" human-readable
8. Batch mode: one timestamp per line for bulk conversion

FAQ

10 vs 13 digits — when to use which?

10 digits is Unix Time (seconds), 13 digits is milliseconds. JavaScript Date.now() returns 13 digits; Java System.currentTimeMillis() also 13. MySQL TIMESTAMP / Linux system time is 10 (seconds). The most common frontend-backend bug is off-by-three-zeros — this tool auto-detects.

Why is 1970-01-01 the start?

Unix Time chose 1970-01-01 00:00:00 UTC as the epoch, just before Unix systems became popular. A 32-bit signed seconds timestamp can represent up to 2038-01-19 (the famous "2038 problem" — 32-bit systems must upgrade to 64-bit).

How does the tool handle timezones?

A timestamp is absolute (no timezone in itself). The same timestamp shows differently depending on display timezone. Timestamp 1700000000: UTC shows 2023-11-14 22:13:20; Beijing time shows 2023-11-15 06:13:20.

How to convert between ISO 8601 and timestamp?

ISO 8601 is a string format: 2026-01-01T08:00:00.000Z (Z = UTC) or 2026-01-01T16:00:00+08:00. JS: new Date("2026-01-01T08:00:00Z").getTime() / 1000. APIs should use ISO 8601 strings (readable, carries timezone); databases store timestamps (compact).

Does DST affect timestamps?

Timestamps are absolute, unaffected by DST. But displayed local time jumps. China dropped DST in 1992. For US/EU data, beware DST transition days: some moments do not exist (spring forward) or repeat (fall back). Libraries (date-fns, Luxon) handle this.

Use cases

• Backend log triage: timestamps in logs (e.g. 1700000000) reverse-lookup actual time
• API debugging: confirm seconds vs milliseconds during frontend-backend integration
• Database time check: convert created_at / updated_at to readable
• Scheduled tasks: verify cron next-run timestamp is correct
• Cross-timezone meetings: same timestamp shows local time for users in different zones

Use cases

Backend log triage, frontend-backend time field, database time check, scheduled tasks, cross-timezone time. Backend, frontend, QA, ops. Auto seconds/milliseconds detection, multi-timezone display, ISO 8601 bidirectional, relative time are the differentiators.