What is a Unix Timestamp?
A Unix timestamp (also called Epoch time, POSIX time, or Unix time) is a way of tracking time as a running total of seconds. The count starts at the Unix Epoch on January 1, 1970, at 00:00:00 UTC. At this moment, the Unix timestamp was 0. Since then, it has been counting up by one every second.
For example, the timestamp 1700000000 represents November 14, 2023, at 22:13:20 UTC. This system provides a consistent, timezone-independent way to represent points in time.
Why Unix Timestamps Are Used
Database Storage
Timestamps are integers, making them efficient to store and index. They take up less space than formatted date strings and are faster to compare and sort.
API Communication
Many APIs use Unix timestamps because they're unambiguous. Unlike date strings, which can be interpreted differently based on format and timezone, timestamps have one meaning everywhere.
Timezone Independence
Timestamps represent a specific moment in time regardless of timezone. Converting to local time is done at display time, not storage time, preventing timezone-related bugs.
Date Arithmetic
Calculating time differences is simple math with timestamps. Subtracting one from another gives you the exact number of seconds between two events.
Seconds vs Milliseconds
Unix Timestamp (Seconds)
The traditional Unix timestamp counts seconds since the epoch. It's a 10-digit number (until 2286) and is used in many systems including Unix/Linux commands, PHP, and many databases.
JavaScript Timestamp (Milliseconds)
JavaScript's Date.now() returns milliseconds since the epoch, a 13-digit number. This provides more precision and is used in JavaScript, Java, and some modern APIs.
How to Tell the Difference
Count the digits: 10 digits is seconds, 13 digits is milliseconds. Or look at the value: if it's around 1700000000, it's seconds; if it's around 1700000000000, it's milliseconds.
Common Timestamp Operations
Get Current Timestamp
In most programming languages, getting the current timestamp is a single function call. In JavaScript: Math.floor(Date.now() / 1000)
Add or Subtract Time
To add 24 hours to a timestamp, add 86400 (24 * 60 * 60 seconds). This simple arithmetic works for any time calculation.
Compare Dates
Simply compare the numeric values. A larger timestamp is a later date. This is much simpler than parsing and comparing date strings.
The Year 2038 Problem
32-bit systems store Unix timestamps as signed integers, which will overflow on January 19, 2038. Most modern 64-bit systems use 64-bit timestamps, which won't overflow for billions of years.
Privacy and Security
All timestamp conversion happens entirely in your browser using JavaScript's Intl API for timezone handling. No data is sent to any server, making this tool safe for working with any timestamps.
Common Use Cases
Log File Analysis
Convert Unix timestamps in log files to human-readable dates for debugging and analysis.
API Development
Verify timestamp values when building or debugging APIs that use epoch time.
Database Queries
Convert dates to timestamps for database queries or understand timestamp values in query results.
JWT Token Inspection
Decode expiration times (exp) and issued-at times (iat) in JSON Web Tokens.
Event Scheduling
Calculate timestamps for scheduling future events or determining time until an event.
Cross-Timezone Coordination
Convert between timestamps and dates in different timezones for global team coordination.
Worked Examples
Timestamp to Date
Input
1700000000
Output
Date: November 14, 2023, 22:13:20 UTC ISO: 2023-11-14T22:13:20.000Z
The Unix timestamp 1700000000 is converted to its human-readable date representation in various formats.
Date to Timestamp
Input
2024-01-01T00:00:00Z
Output
Seconds: 1704067200 Milliseconds: 1704067200000
The ISO date string for January 1, 2024, at midnight UTC is converted to Unix timestamp in both seconds and milliseconds.
Frequently Asked Questions
How do I know if a timestamp is in seconds or milliseconds?
Count the digits. Timestamps in seconds are 10 digits (until 2286), while millisecond timestamps are 13 digits. If the value is around 1.7 billion, it is seconds; if around 1.7 trillion, it is milliseconds.
Why do some timestamps appear negative?
Negative timestamps represent dates before January 1, 1970 (the Unix epoch). For example, -86400 represents December 31, 1969.
What timezone is used for Unix timestamps?
Unix timestamps are always in UTC. They represent a specific moment in time independent of timezone. When displaying, you convert to the desired timezone.
What is the maximum Unix timestamp?
On 64-bit systems, the maximum is 9223372036854775807, far in the future. On 32-bit systems, the maximum is 2147483647 (January 19, 2038), which is the Y2038 problem.
Is my data sent to any server?
No, all conversion happens locally in your browser using JavaScript. Your timestamps and dates never leave your device.
How do I get the current Unix timestamp?
Click "Now" in the tool to insert the current timestamp. In code: JavaScript uses Math.floor(Date.now()/1000), Python uses time.time(), and Unix/Linux uses the date +%s command.