Timestamps
A timestamp’s format, unit and reference clock determine how to interpret it. Unix seconds and milliseconds use different scales; a browser performance reading is relative to a time origin rather than a formatted calendar date.
Use the universal time converter to read ISO 8601 and Unix values as local dates and times. The High Resolution Time article explains why measuring code execution calls for a monotonic clock.
Universal time converter
Convert dates and times between time zones. Understand UTC offsets, daylight saving and date changes, with JavaScript and Python conversion examples.
Meet Our New Universal Time Converter
Compare dates and times across time zones with our free converter. Check daylight-saving changes, read Unix timestamps and share a conversion link.
W3C Updates High Resolution Time Draft: What JavaScript Performance Measurements Need to Get Right
The W3C published a High Resolution Time Working Draft on November 6, 2026. Here is what performance.now(), timeOrigin and timer privacy mean for developers.