Epoch Time Converter
Convert Unix/Epoch timestamps to human-readable dates, or convert dates back to epoch seconds and milliseconds.
Supports negative timestamps (dates before Jan 1, 1970) and large future values.
What is epoch time?
Epoch time (also called Unix time or POSIX time) is the number of seconds that have elapsed since January 1, 1970 at 00:00:00 UTC, not counting leap seconds. It gives developers a simple, language-neutral way to store and exchange dates.
Because a timestamp is just a number, it works well in databases, APIs, logs, analytics tools, and distributed systems. A single integer is often easier to compare, sort, and transmit than a long date string.
How to use this epoch time calculator
1) Convert Epoch to Date
Enter a timestamp in the first field and click Convert Epoch → Date. If your input has 13 digits (for example, JavaScript-style timestamps), check the milliseconds box first.
- Shows local time based on your browser/device timezone
- Shows UTC time for global consistency
- Shows ISO 8601 format for APIs and structured data
- Provides a human relative description like “2 days ago”
2) Convert Date to Epoch
Pick a date/time using the datetime input and click Convert Date → Epoch. You will get both:
- Epoch seconds (10-digit style, common in backend systems)
- Epoch milliseconds (13-digit style, common in JavaScript)
If you are matching server logs or cloud systems, check the option to interpret the input as UTC.
Seconds vs milliseconds: why it matters
This is the most common source of timestamp errors. If you pass milliseconds to a system expecting seconds, the date may appear thousands of years in the future. If you pass seconds where milliseconds are expected, your date can appear in 1970.
- Seconds: 1704067200
- Milliseconds: 1704067200000
A quick check: milliseconds values are usually 13 digits, while seconds are usually 10 digits (for present-day timestamps).
Time zones, UTC, and daylight saving time
Epoch itself is timezone-agnostic, but human-readable formatting is not. The same epoch value displays differently depending on location. That is why engineers often store timestamps as epoch/UTC and only convert to local time in the user interface.
Daylight saving transitions can also create confusing local times. Using UTC in storage and transport helps avoid ambiguity.
Common use cases
- Debugging application logs
- Converting API payload timestamps
- Database migration and ETL validation
- Scheduling, cron troubleshooting, and job monitoring
- Security analysis and incident timelines
Quick tips for reliable timestamp handling
- Always label your unit (sec vs ms) in code and docs.
- Prefer ISO 8601 for readable interchange when possible.
- Store UTC internally; convert to local time only for display.
- Add tests around timezone boundaries and DST changes.
- When integrating APIs, verify examples in official documentation.
Final thought
Epoch time looks simple, but tiny unit or timezone mistakes can cause major bugs. Use this calculator to quickly validate conversions before deploying data pipelines, backend logic, or frontend date rendering.