Unix Timestamp Converter

Frequently Asked Questions

How does the tool know whether my input is seconds or milliseconds?

It checks the magnitude: values greater than 10 billion (10,000,000,000) are treated as milliseconds because valid second-based timestamps will not exceed that until the year 2286. All smaller values are treated as seconds.

What is the Unix epoch?

January 1, 1970, 00:00:00 UTC. All Unix timestamps count forward (or backward for negative values) from this fixed reference point.

Why do JavaScript and Python give different numbers for the 'same' timestamp?

JavaScript's Date.getTime() returns milliseconds; Python's time.time() returns seconds (as a float). Multiply Python's result by 1,000 or divide JavaScript's by 1,000 to compare them.

What is ISO 8601 format?

A standardized date-time string such as 2024-04-30T00:00:00.000Z. The Z suffix means UTC. ISO 8601 is the international standard for machine-readable date-time interchange and is understood by all modern programming languages and databases.

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How This Calculator Works

Choose a direction: Timestamp → Date or Date → Timestamp. When converting a timestamp, the tool detects whether it is in seconds or milliseconds automatically: inputs greater than 10 billion are treated as milliseconds (13 digits), all others as seconds (10 digits). Results are shown simultaneously in UTC, your local time, and ISO 8601 format. The "Now" button inserts the current Unix timestamp in seconds at the moment you press it.

What Is a Unix Timestamp?

A Unix timestamp (also called epoch time or POSIX time) is the number of seconds elapsed since the Unix epoch: January 1, 1970, 00:00:00 UTC. It is the universal time format for software because it is a single integer that uniquely represents any moment in time, free from time zones, daylight saving, calendar quirks, and locale formatting. JavaScript's Date.getTime(), Python's time.time(), and most database TIMESTAMP columns return Unix epoch values, often in milliseconds.

Common Timestamp Formats

Seconds since epoch (10 digits): e.g. 1,714,435,200. Standard in Unix/Linux, log files, JWT exp claims, and HTTP headers.

Milliseconds since epoch (13 digits): e.g. 1,714,435,200,000. Standard in JavaScript, Java, and many modern databases.

Microseconds (16 digits): used in high-precision timestamps (PostgreSQL, scientific data).

Nanoseconds (19 digits): used in Go's time.Time, Linux kernel, and high-frequency trading.

ISO 8601: human-readable string, e.g. 2024-04-30T00:00:00.000Z. The international standard for date-time interchange.

Notable Timestamps

0: January 1, 1970, 00:00:00 UTC - the Unix epoch itself.

1,000,000,000: September 9, 2001, 01:46:40 UTC - the "billion-second" milestone.

1,234,567,890: February 13, 2009, 23:31:30 UTC - celebrated by Unix admins worldwide.

2,000,000,000: May 18, 2033, 03:33:20 UTC.

2,147,483,647: January 19, 2038, 03:14:07 UTC - the "Y2038 problem" limit for 32-bit signed integers.

The Year 2038 Problem

Many older 32-bit systems store Unix timestamps as signed 32-bit integers, which overflow at 2,147,483,647 on January 19, 2038. After that moment, affected systems may crash or wrap to 1901. Modern 64-bit systems extend the safe range to about 292 billion years, but legacy embedded systems - industrial controllers, banking infrastructure, and some IoT firmware - still face migration work before 2038. The Y2038 problem is the successor to the Y2K issue and affects a narrower but still significant set of systems.

Unix Timestamp Converter

Frequently Asked Questions

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