Convert Unix epoch timestamps to human dates and back instantly. Paste seconds or milliseconds to see UTC, local time, and ISO 8601, or pick a date to get both timestamp formats — all processing stays in your browser.
Technical Specifications
Epoch handling and formatting rules used for every conversion.
| Specification |
Details |
| Epoch reference |
Unix time counts from 1970-01-01 00:00:00 UTC. All math uses JavaScript Date number of milliseconds since epoch. |
| Supported inputs |
Timestamp seconds (10 digits typical), milliseconds (13 digits), or ISO 8601 / datetime-local strings |
| Auto detection |
Abs value >= 1e12 treated as ms, >= 1e10 as ms if > year 2286 guard, else s. Manual override via dropdown forces seconds or milliseconds. |
| Outputs |
Unix seconds (floor ms/1000), Unix ms, local string, UTC string, ISO 8601 UTC, and relative time like 2 days ago |
| Date parsing |
datetime-local interpreted as local time; ISO string with Z parsed as UTC; offset-aware ISO preserved to UTC internally |
| Valid range |
Limited by JS Date: approx ±100,000,000 days from epoch (±273,790 years). Out-of-range shows error. |
| Precision |
Millisecond precision. Seconds output is integer floor. ISO includes .000 ms. |
| Processing location |
100% client-side JavaScript in your browser memory; nothing is uploaded |
| Export |
Copy full report or any single field, or download a plain-text report with all formats |
| Usage limit |
None — run unlimited conversions for free, no signup required |
Understanding Unix Timestamps
A Unix timestamp counts seconds or milliseconds since 1970-01-01 00:00:00 UTC — the Unix Epoch. Databases, server logs, and JavaScript use it because it is timezone-free and sortable as an integer, unlike formatted dates that vary by locale.
Seconds vs milliseconds
Classic Unix time is seconds, typically 10 digits like 1704067200 for 2024-01-01. JavaScript Date.now() returns milliseconds, 13 digits like 1704067200000. Mixing them shifts dates by a factor of 1000, so detection matters: 1704067200 seconds is Jan 1 2024, but read as milliseconds it is Jan 20 1970. Set the dropdown to Seconds or Milliseconds when you know the source, or leave Auto for guessing by magnitude.
UTC, local, and ISO 8601
The same instant looks different by zone. 2024-01-01T00:00:00.000Z is midnight UTC, but in New York it is 2023-12-31 19:00 local. ISO 8601 with Z always means UTC, while datetime-local input has no zone and is treated as your computer local time. This tool shows both simultaneously so you can verify offsets before storing dates. See also the Time Zone Converter for cross-zone scheduling and the Date Difference Calculator for day counts.
When to use which format
Use seconds for most back-end logs, MySQL timestamps, and Python time.time(). Use milliseconds for JavaScript, Java, and Firebase. Use ISO 8601 for APIs and JSON payloads because it is human-readable and unambiguous. Convert through this tool before pasting into database queries to avoid off-by-1000 bugs.
Honest limitations
JavaScript Date cannot represent dates far beyond ±273,790 years and does not count leap seconds — it treats every day as 86,400 seconds. Very large or negative timestamps before 1970 work but calendar formatting may be approximate for pre-1582 Gregorian adoption. For business day differences use a calendar-specific calculator rather than raw epoch subtraction.
Privacy and Client-Side Security
Privacy Guarantee: All conversions occur locally inside your browser. Your timestamps and dates are never transmitted, stored, or recorded on remote servers.
Many online converters send timestamps to a server for lookup, which leaks log data. TinyToolzz keeps everything in-page: epoch parsing, Date construction, and string formatting run with plain JavaScript operations.
Because nothing is uploaded, there is no waiting, no account, and no copy of your dates retained anywhere. Your values exist only in the tab's memory and are discarded when you close the page or click Clear.