Can Unix timestamps be negative?

Yes. Negative timestamps represent dates before January 1, 1970. For example, timestamp -86400 represents December 31, 1969. This allows representing historical dates in the same format.

What is the difference between seconds and milliseconds timestamps?

Unix timestamps are traditionally in seconds (10 digits currently). JavaScript and many modern APIs use milliseconds (13 digits). To convert: seconds x 1000 = milliseconds. If a timestamp has 13 digits, it is likely in milliseconds.

Does the timestamp account for leap seconds?

Unix time does NOT account for leap seconds. Each Unix day is exactly 86,400 seconds. When a leap second occurs, Unix time either repeats a second or skips one, depending on implementation. This means Unix time can differ from UTC by up to 1 second.

Why was 1970 chosen as the epoch?

The Unix operating system was being developed at Bell Labs in the late 1960s and early 1970s. January 1, 1970 was chosen as a convenient recent date that minimized the number of bits needed to represent contemporary timestamps in the 32-bit systems of the era.

Unix Timestamp Converter

Convert Unix timestamps to dates and dates to Unix timestamps

Unix Timestamp Converter

Convert between Unix timestamps and dates

Enter a Unix timestamp (seconds)

Unix Timestamp

Formula

Date = new Date(timestamp x 1000)

What Is a Unix Timestamp?

A Unix timestamp (also called epoch time or POSIX time) is the number of seconds that have elapsed since January 1, 1970 00:00:00 UTC — the Unix epoch. It's the universal standard for representing dates and times in programming, databases, APIs, and system logs. Because it's just a number, it's timezone-independent and easy to store, sort, and compare across any programming language or operating system.

This converter instantly translates any Unix timestamp to a human-readable date and time (in your local timezone), and converts any date/time back to a Unix timestamp. It also supports millisecond timestamps used in JavaScript's Date.now() — values greater than 10 digits are automatically detected as millisecond-precision timestamps and handled accordingly.

How to Use the Unix Timestamp Converter

Enter a Unix timestamp (e.g., 1700000000) in the input field to convert it to a human-readable date and time.
Or enter a date and time to convert it to a Unix timestamp.
Click Convert to see the result.
Millisecond timestamps are automatically detected — if your value is greater than 10 digits, the tool treats it as milliseconds (as used by JavaScript's Date.now()).

Formulas & Reference

Unix timestamp = seconds since 1970-01-01 00:00:00 UTC

Current timestamp (approx):
  ~1,700,000,000  (November 2023)
  ~1,745,000,000  (April 2025)

JavaScript:
  Date.now()                          // milliseconds
  Date.now() / 1000                   // seconds (float)
  Math.floor(Date.now() / 1000)       // integer seconds

Convert timestamp to date (JavaScript):
  new Date(timestamp * 1000).toISOString()

Year 2038 problem:
  32-bit signed int max = 2,147,483,647
  = January 19, 2038 03:14:07 UTC

Unix timestamps are always in UTC. When displaying to users, convert to local time. JavaScript's Date object uses milliseconds internally, so multiply by 1000 when passing a Unix timestamp (seconds) to new Date(), and divide by 1000 when converting Date.now() back to seconds.

Timestamp Examples

Timestamp 0 — The Epoch

The value 0 corresponds to January 1, 1970 00:00:00 UTC — the starting point of Unix time, known as the Unix epoch. Every timestamp is measured relative to this moment.

Timestamp 1,000,000,000 — The Billion-Second Milestone

September 9, 2001 01:46:40 UTC. This was a celebrated milestone in the developer community — the moment Unix time hit one billion seconds. Some systems around the world held countdown events.

Timestamp 1,700,000,000 — November 2023

Approximately November 14, 2023 22:13:20 UTC. A useful reference point: timestamps in the 1.7 billion range correspond to late 2023. As of April 2025, current timestamps are around 1.745 billion.

Frequently Asked Questions

Why does Unix time start on January 1, 1970?▾

When Unix was developed in the early 1970s, the engineers needed a fixed reference point. January 1, 1970 00:00:00 UTC was chosen as a practical, round starting date. It predates Unix itself slightly, which makes it a clean epoch for calculating elapsed time across all of Unix history.

What is the Year 2038 problem?▾

Many older systems store Unix timestamps as 32-bit signed integers, which max out at 2,147,483,647. That value corresponds to January 19, 2038 03:14:07 UTC. After that moment, a 32-bit counter would overflow and roll back to a large negative number — potentially causing crashes or incorrect dates. Modern systems use 64-bit integers and won't face this issue for hundreds of billions of years.

What is the difference between a seconds timestamp and a milliseconds timestamp?▾

A standard Unix timestamp counts seconds since the epoch (e.g., 1700000000). JavaScript's Date.now() returns milliseconds instead (e.g., 1700000000000 — three extra zeros). To convert from milliseconds to seconds, divide by 1000. To convert a seconds timestamp for use in JavaScript's new Date(), multiply by 1000. This converter auto-detects values over 10 digits as millisecond timestamps.

Is a Unix timestamp affected by timezone?▾

No. Unix timestamps represent an absolute point in time in UTC. They are completely timezone-independent. The same timestamp value means the same instant everywhere on Earth. Timezone conversion only happens when you display the timestamp to a human user — the underlying number never changes.

What does a negative Unix timestamp mean?▾

A negative Unix timestamp represents a date before the Unix epoch — before January 1, 1970 00:00:00 UTC. For example, -86400 is December 31, 1969 00:00:00 UTC (one day before the epoch). Negative timestamps are valid and supported by most modern systems and programming languages.