Free Developer Utility
Unix Timestamp Converter
Convert Unix timestamps to human-readable dates and back, explore every date format, convert across timezones, calculate differences, and discover relative times - all in real time, entirely in your browser.
Live Converter
Timestamp & Date Conversion
Advanced Tool
Date Difference Calculator
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Add / Subtract Time
Developer Guide
Everything About Unix Timestamps & Date Conversion
A complete reference for developers, system administrators, and data engineers working with time in software systems.
What is a Unix Timestamp?
A Unix timestamp (also called Unix time, POSIX time, or epoch time) is the number of seconds that have elapsed since January 1, 1970, at 00:00:00 UTC - a moment known as the Unix epoch. It is a single integer that uniquely identifies any moment in time without ambiguity across timezones. Negative values represent dates before 1970.
Unix Timestamp vs Human Date
Human-readable dates like 2024-11-14 12:30:00 are convenient to read but ambiguous without a timezone. A Unix timestamp like 1731585000 is unambiguous - it always refers to the same moment in time everywhere on Earth. Databases, APIs, and logging systems use Unix timestamps for sorting, arithmetic, and cross-timezone calculations.
How Unix Time Works
Unix time counts seconds continuously, ignoring leap seconds (with some exceptions in modern systems). One day = 86,400 seconds. One week = 604,800 seconds. The 32-bit signed integer representation will overflow at timestamp 2,147,483,647 - January 19, 2038, known as the Year 2038 problem. Modern systems use 64-bit integers, which won't overflow for billions of years.
UTC vs GMT vs Local Time
UTC (Coordinated Universal Time) is the global time standard, kept by atomic clocks. GMT (Greenwich Mean Time) is a timezone aligned to UTC but historically observed in the UK. They differ in that UTC is a standard, not a timezone. "Local time" is the clock time in your geographic location, which may be offset from UTC by hours or fractions of hours depending on your region and DST rules.
Common Unix Timestamp Examples
0- Thu Jan 01 1970 00:00:00 UTC (the epoch)1000000000- Sat Sep 08 2001 21:46:40 UTC1234567890- Fri Feb 13 2009 23:31:30 UTC1700000000- Wed Nov 14 2023 22:13:20 UTC2000000000- Wed May 18 2033 03:33:20 UTC2147483647- Tue Jan 19 2038 03:14:07 UTC (32-bit max)
Developer Use Cases
Unix timestamps are used everywhere in software: database record creation and modification times, JWT token expiration (exp, iat), HTTP cache headers, log file correlation, API rate limiting windows, session expiry, file modification times, event scheduling, performance benchmarking, and distributed system synchronization. Most programming languages provide built-in functions to work with them.
ISO 8601 & RFC Formats
ISO 8601 (2024-11-14T22:13:20Z) is the international standard for date/time representation used in XML, JSON, HTML, and most modern APIs. RFC 2822 (Wed, 14 Nov 2024 22:13:20 +0000) is used in email headers and HTTP. RFC 3339 is a stricter profile of ISO 8601 used in internet protocols and is the format used in RSS, Atom feeds, and OpenAPI specifications.
Timezone Conversion Fundamentals
Every Unix timestamp is in UTC. To display it in a local time, you add the timezone's UTC offset. For example, UTC+5:30 (India) means adding 5 hours and 30 minutes. Daylight Saving Time (DST) can change a timezone's offset by 1 hour during summer months. IANA timezone names (like America/New_York) encode DST rules automatically, whereas fixed offsets (like UTC-5) do not.
FAQs
Unix Timestamp Frequently Asked Questions
What is Unix time / epoch time?
Unix time is the number of seconds elapsed since the Unix epoch: January 1, 1970, 00:00:00 UTC. It is timezone-independent and is the de facto standard for representing time in computing systems worldwide.
How do I get the current Unix timestamp in different languages?
JavaScript: Math.floor(Date.now() / 1000) or Date.now() for milliseconds. Python: import time; time.time(). PHP: time(). Go: time.Now().Unix(). Java: System.currentTimeMillis() / 1000. SQL: UNIX_TIMESTAMP() (MySQL) or EXTRACT(EPOCH FROM NOW()) (PostgreSQL).
What is the difference between Unix seconds and milliseconds?
Most Unix timestamps are measured in seconds. JavaScript's Date.now() returns milliseconds (1000× the seconds value). When a 13-digit timestamp appears (e.g., 1700000000000), it is in milliseconds. A 10-digit timestamp is in seconds. This converter handles both - check the "Input is milliseconds" toggle when using ms values.
What will happen at Unix timestamp 2147483647?
That value - January 19, 2038, 03:14:07 UTC - is the maximum value of a 32-bit signed integer. Systems still using 32-bit integers to store timestamps will overflow (the Year 2038 Problem). Modern 64-bit systems are not affected and can store timestamps billions of years into the future.
How does this converter handle timezones?
All Unix timestamps are inherently UTC. When displaying in a timezone, this tool uses the browser's native Intl.DateTimeFormat API with IANA timezone identifiers, which correctly handles Daylight Saving Time transitions for each region. The live clock updates every second using requestAnimationFrame.
Does this tool send my data to a server?
No. All conversions, calculations, and timezone lookups run entirely in your browser using the native JavaScript Date and Intl APIs. Nothing is transmitted to any server.
What is ISO 8601 and when should I use it?
ISO 8601 is the international standard for date and time notation: YYYY-MM-DDTHH:mm:ssZ. Use it for APIs, JSON payloads, HTML datetime attributes, and any data that crosses system boundaries. It is unambiguous, sortable as a string, and understood by parsers in every major programming language.
Can I convert negative Unix timestamps?
Yes. Negative Unix timestamps represent dates before the epoch (January 1, 1970). For example, -86400 is December 31, 1969, 00:00:00 UTC. This converter handles negative values correctly across all output formats.