Timestamp Converter — Unix to ISO 8601 in seconds

1. What does this tool do

This free online timestamp converter converts Unix timestamps and date strings to the format you need—seconds, milliseconds, ISO 8601, RFC 2822, or human-readable. Use it as a Unix timestamp converter for developers, logs, and APIs. Pick a display timezone (Local, UTC, or any IANA zone) and paste a timestamp or date. No sign-up, no upload; all in your browser. Ideal for API development, log analysis, databases, or debugging.

2. How to use it

Quick start: Paste a Unix timestamp (e.g. 1709251200 or 1709251200000) or a date string. Select display timezone, then copy Unix seconds, milliseconds, ISO 8601, or human-readable format.

1. Enter input — Type a Unix timestamp (e.g. 1709251200 or 1709251200000) or a date string (e.g. 2024-03-01T12:00:00Z).
2. Select display timezone — Choose Local (browser), UTC, or a common zone (e.g. Asia/Ho_Chi_Minh, America/New_York). ISO 8601 and human-readable formats use this zone.
3. View outputs — Unix seconds, milliseconds, ISO 8601, RFC 2822, and human-readable format appear.
4. Use any format — Copy the format you need (e.g. for API payloads or logs).
5. Reverse — Paste an ISO or RFC 2822 string to get the Unix timestamp.

3. How it works

Numeric input: Values < 1e12 are treated as seconds (covers 1970–33658); values ≥ 1e12 as milliseconds. String input: Passed to Date.parse, which supports ISO 8601, RFC 2822, and common formats. Display timezone: When UTC or Local, ISO 8601 uses toISOString() or local formatting; when a non-UTC zone is selected, ISO 8601 includes the offset. All computation runs entirely in your browser. No data is sent to any server.

4. Use cases & examples

• API development — Convert between formats for request/response.
• Log analysis — Decode Unix timestamps from logs.
• Database — Translate stored timestamps to human dates.
• Debugging — Verify date parsing and timezone handling.
• Documentation — Generate example timestamps for docs.

Example

• 1709251200 (seconds) → 2024-03-01T12:00:00.000Z
• 1709251200000 (milliseconds) → same date
• 2024-03-01 12:00:00 → Unix timestamp + all formats

5. Limitations & known constraints

• Display timezone — You can display outputs in Local, UTC, or selected IANA zones; RFC 2822 remains in UTC.
• Range — Timestamps outside JavaScript Date range may fail.
• Auto-detect — 1e12 threshold for seconds vs ms; ambiguous for values near that.
• String parsing — Depends on Date.parse; non-standard formats may fail.