What is a Unix Timestamp?
A Unix timestamp represents the number of seconds (or milliseconds) that have elapsed since January 1, 1970 (UTC), excluding leap seconds. It's the universal language of time in computing — databases store it, APIs return it, and logs record it.
Seconds vs. Milliseconds: A Common Pitfall
One of the most frequent bugs in backend development is confusing second-precision timestamps with millisecond-precision ones. JavaScript's Date.now() returns milliseconds, while most Unix systems default to seconds. Always check the documentation of the API or database you are working with to confirm which precision is expected. A Unix Timestamp Converter that supports both units lets you toggle between seconds and milliseconds to determine which one matches your expected date. If you see a date far in the future (like year 51377), the timestamp you entered was likely in milliseconds but interpreted as seconds.
Batch Conversion for Large Datasets
Working with logs or database dumps that contain hundreds of timestamps? Manually converting each one is impractical. Use a Batch Timestamp Converter — paste multiple values at once and get them all converted in a single view, with each timestamp shown alongside its human-readable equivalent. This is particularly useful during data migration projects where you need to validate that all dates were correctly transformed during an ETL process.
Timezones Made Easy
A timestamp is always UTC, but your users aren't. Displaying times in the correct timezone is crucial for UX. Our tool supports all IANA timezone names so you can preview exactly what your users will see. When building international applications, convert timestamps to the user's local timezone on the client side rather than sending pre-converted strings from the server. This keeps your API responses consistent and lets each user see times in their own zone without additional server-side logic.
Converting Between Timestamps and ISO 8601
Unix timestamps and ISO 8601 strings are the two most common time formats in web APIs. Timestamps are compact and timezone-agnostic — they represent an instant without ambiguity. ISO 8601 strings like 2026-06-07T15:30:00Z are human-readable and support timezone offsets. Converting between the two is a routine task during API integration and debugging. A Timestamp to Date Converter handles this bidirectionally, accepting timestamps in seconds or milliseconds and returning the equivalent ISO 8601 string, or vice versa. This is especially useful when logs record timestamps but your monitoring dashboard displays dates — you can translate between formats in seconds without leaving your browser.
Timestamps in Database Systems
Each database handles timestamps differently, and knowing these differences prevents subtle bugs. In MySQL, the TIMESTAMP type stores values internally as Unix timestamps and automatically converts to the session timezone on retrieval, while DATETIME stores the literal value without timezone conversion. PostgreSQL stores timestamps as either TIMESTAMP WITH TIME ZONE (which stores UTC and converts on retrieval) or TIMESTAMP WITHOUT TIME ZONE (which stores the literal value). MongoDB uses 64-bit integers for its default timestamp and stores dates as BSON Date objects internally representing milliseconds since the Unix epoch. When migrating data between systems, our Batch Timestamp Converter is invaluable — you can paste every timestamp from an exported column and confirm they all represent the correct human-readable dates before importing into the new system.
Calculating Date Ranges and Durations
Working with time differences is a fundamental backend task — whether calculating session duration, measuring API response times, or computing subscription end dates. Subtracting two Unix timestamps gives the difference in seconds, which you can then convert into minutes, hours, or days. For more complex operations like adding business days or computing intervals across timezone boundaries, a Date Duration Calculator provides accurate results without writing custom logic. For performance monitoring, our Time Duration Calculator helps compute time spans between two timestamps, useful for analysing latency, SLA compliance, or user session lengths across different time periods.
