What is Unix Timestamp Converter?
A Unix timestamp (epoch time) is the number of seconds elapsed since 00:00:00 UTC on Thursday, 1 January 1970. It is the de-facto universal time format in computing — used in databases, APIs, JWT tokens, cron jobs, file systems, and every major programming language. A 10-digit number represents seconds; a 13-digit number is milliseconds (as returned by JavaScript's Date.now()). Negative values represent dates before the epoch. ISO 8601 (e.g. 2025-01-01T00:00:00.000Z) is the safest interchange format because it encodes the timezone offset, eliminating locale ambiguity.
Best For
Fast browser-based workflows that do not require uploading files to a server.
Privacy
Your data stays on your device because processing happens locally in the browser.
Access
Free to use, no account required, and available at https://www.filemint.dev/tools/timestamp-converter.
Deep Dive: Unix Timestamp Converter
A Unix timestamp (epoch time) is the number of seconds elapsed since 00:00:00 UTC on Thursday, 1 January 1970. It is the de-facto universal time format in computing — used in databases, APIs, JWT tokens, cron jobs, file systems, and every major programming language. A 10-digit number represents seconds; a 13-digit number is milliseconds (as returned by JavaScript's Date.now()). Negative values represent dates before the epoch. ISO 8601 (e.g. 2025-01-01T00:00:00.000Z) is the safest interchange format because it encodes the timezone offset, eliminating locale ambiguity.
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Privacy Architecture
This tool uses client-side WebAssembly to ensure your data never touches a server. Secure, fast, and privacy-focused by design.
Core Capabilities
- Auto-detect seconds vs milliseconds input
- Convert Unix timestamp → ISO 8601, UTC, local, RFC 2822, relative time
- Convert any date/time → Unix seconds and milliseconds
- Live ticking current timestamp with one-click copy
- Timezone selector: UTC, Local, and major world cities
- Negative timestamp support (pre-1970 dates)
- Copy any result format instantly
- 100% browser-based — no server, no uploads
Why It Matters
- Debug Faster: Decode cryptic database timestamps without writing code.
- API Ready: Convert expiry fields to readable dates or back to numbers.
- Time Zone Safe: See any timestamp in UTC, local time, or any major city.
- Zero Friction: No sign-up, no limits, works offline after first load.
Quick Start Guide
Paste a Unix timestamp (seconds or milliseconds) into the Convert tab.
The tool auto-detects the unit and shows ISO 8601, UTC, local, RFC 2822, and relative time.
Use the timezone selector to view the timestamp in any major timezone.
Switch to Date → Unix to pick a date and get the corresponding epoch number.
Open Live Clock to copy the current Unix timestamp in real time.
Questions?
Technical Architecture
Seconds vs Milliseconds Detection
Timestamps above 9,999,999,999 (10 digits or more) are treated as milliseconds; below that threshold they are treated as seconds. This threshold corresponds to November 2001 in Unix seconds, making it a safe boundary for any real-world modern timestamp.
Intl.DateTimeFormat & Timezone Support
All timezone-aware formatting uses the browser-native `Intl.DateTimeFormat` API backed by the CLDR timezone database. This ensures DST-accurate results for all major zones without adding any external dependency.
Relative Time Calculation
Relative time is computed by subtracting `Date.now()` from the target timestamp, bucketing the absolute difference into seconds, minutes, hours, days, months, or years. The sign of the difference determines "ago" vs "from now".
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