Unix Timestamp Converter
Convert between Unix timestamps and human-readable dates. Supports seconds, milliseconds, and ISO 8601 formats.
Supports both seconds and milliseconds (auto-detected)
How to Use the Timestamp Converter
- Enter a Unix timestamp (seconds or milliseconds) to convert it to a human-readable date.
- Alternatively, select a date and time to get its Unix timestamp equivalent.
- Choose your preferred output format: ISO 8601, locale string, or relative time.
- Copy the converted result for use in your code or documentation.
What is a Unix Timestamp?
A Unix timestamp (also called Epoch time or POSIX time) represents the number of seconds that have elapsed since January 1, 1970 00:00:00 UTC, known as the Unix Epoch. This integer-based system provides a universal, timezone-independent way to represent a specific moment in time. For example, the timestamp 1700000000 corresponds to November 14, 2023 at 22:13:20 UTC. Unix timestamps are fundamental to software development. They are used in database records, log files, API responses, authentication tokens (JWT expiration), file systems, and cron scheduling. Most programming languages and databases natively support Unix timestamps. They are particularly useful for computing time differences, sorting events chronologically, and avoiding timezone ambiguity. There are important variations to be aware of. Some systems use milliseconds (13-digit timestamps like those in JavaScript's Date.now()) while others use seconds (10-digit, standard Unix). The Year 2038 problem affects systems using 32-bit signed integers for timestamps, as they will overflow on January 19, 2038. Most modern systems use 64-bit integers, which extends the range far beyond practical limits. When working with timestamps in security contexts, always validate that token expiration times and certificate validity dates are correctly interpreted.
Frequently Asked Questions
Unix timestamps in seconds are 10 digits (e.g., 1700000000) and are the traditional format used by most Unix systems, C, Python, and PHP. Millisecond timestamps are 13 digits (e.g., 1700000000000) and are common in JavaScript, Java, and many modern APIs. Always check which format a system expects to avoid bugs.
Systems storing Unix timestamps as 32-bit signed integers will overflow on January 19, 2038 at 03:14:07 UTC. The maximum value (2,147,483,647) will wrap to a negative number, potentially causing dates to jump to 1901. Modern 64-bit systems are not affected, but legacy embedded systems and databases may need updates.
JWTs use Unix timestamps in the exp (expiration), iat (issued at), and nbf (not before) claims to control token validity. These are always in seconds, not milliseconds. Incorrect timestamp handling in token validation can lead to security vulnerabilities like accepting expired tokens or tokens not yet valid.