Unix Timestamp Converter

Unix Timestamp Converter: Understanding Epoch Time

A Unix timestamp (also called epoch time) is the number of seconds that have elapsed since 00:00:00 UTC on January 1, 1970 - the "Unix epoch." Almost every programming language, database, and API uses this format internally to store and compare dates, because a single integer is far easier to sort, subtract, and store than a formatted date string. This calculator converts a raw timestamp into a readable date, and converts a date you pick back into its equivalent timestamp.

The Formula

Converting a timestamp to a date is just arithmetic on top of the epoch:

$$date = epoch_{1970\text{-}01\text{-}01} + timestamp_{seconds}$$

Going the other direction, converting a calendar date and time back to a timestamp is the same operation in reverse - count the number of seconds between the epoch and that moment in UTC.

If your timestamp is in milliseconds instead of seconds (common in JavaScript's Date.now()), divide by 1000 first:

$$timestamp_{seconds} = \frac{timestamp_{milliseconds}}{1000}$$

Worked Example

Suppose you have the timestamp 1751500000 (in seconds).

1. Start from the epoch: 1970-01-01 00:00:00 UTC.
2. Add 1,751,500,000 seconds to it.
3. That lands on Wednesday, 2025-07-02 23:46:40 UTC.

Going the other way: if you pick the date 2026-01-01 at 00:00 UTC, the calculator counts the seconds from the epoch to that moment and returns the timestamp 1767225600.

How to Use This Calculator

• To convert a timestamp to a date: enter the numeric Unix Timestamp, choose whether it's in seconds or milliseconds, and the calculator shows the human-readable date (UTC), the day of the week, the ISO 8601 string, and a relative description like "3 days ago."
• To convert a date to a timestamp: pick a date and, optionally, an hour and minute (24-hour, UTC), and the calculator shows the equivalent Unix timestamp in both seconds and milliseconds.
• Both directions are calculated at once, so you can use whichever input matches what you're working with.

Common Uses for Unix Timestamps

• Debugging APIs and logs: Server logs and API responses frequently store created_at/updated_at fields as raw timestamps - converting them to a readable date is one of the most common developer tasks.
• Database queries: Comparing or filtering rows by date range is often faster as an integer timestamp comparison than a string date comparison.
• Scheduling and expiry: Tokens, cache entries, and cookies commonly store an expiry time as a Unix timestamp.
• Cross-timezone consistency: Because a Unix timestamp is always UTC-based, it avoids the ambiguity of comparing dates across different local timezones.

Things to Watch Out For

• Seconds vs. milliseconds: The single most common mistake is feeding a millisecond timestamp (13 digits, e.g. 1751500000000) into a tool expecting seconds (10 digits, e.g. 1751500000) - always double-check the unit before converting.
• The Year 2038 problem: Systems that store timestamps as a signed 32-bit integer will overflow on 2038-01-19 - modern 64-bit systems (and this calculator) aren't affected, but it's worth knowing about when working with older systems.
• Time zones: This calculator always works in UTC. If you need a local time, add or subtract your timezone's offset from the UTC result.

Conclusion

Unix timestamps are the backbone of how computers store and compare time, precisely because they strip away timezones and formatting ambiguity down to a single number. Whether you're debugging an API response, checking when a token expires, or scheduling a job, being able to quickly convert between a timestamp and a readable date saves time and avoids off-by-one-timezone mistakes.