GPS time converter
GPS receivers and logs give time as a week number and seconds into that week, counted from 6 January 1980 without leap seconds. Type a UTC date and time, a GPS week with seconds of week, or a plain count of GPS seconds, and the converter shows all of them together with the leap-second offset between GPS time and UTC.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
Type one of three forms into the box:
- a UTC date and time:
2026-01-01 12:30:00, or only a date for midnight;
- a GPS week and seconds of week, separated by a space:
2399 345618;
- GPS seconds since the start of GPS time:
1451260818.
All the other forms appear in the results, plus the day of the GPS week, the leap-second offset and the 10-bit week number.
How it works
- GPS time 0 is 1980-01-06 00:00:00 UTC.
- UTC → GPS: seconds since that moment + the leap seconds added up to that date.
- GPS seconds → week = ⌊seconds ÷ 604,800⌋, seconds of week = the remainder.
- GPS → UTC: subtract the leap seconds that apply at that GPS time. During an inserted leap second the UTC clock shows 23:59:60.
The leap-second table holds the 18 leap seconds added from 1981 to 2016.
Worked example
1 January 2026, 00:00:00 UTC is 16,797 days after 6 January 1980, or 2,399 weeks and 4 days.
- GPS week: 2399.
- Seconds of week: 4 × 86,400 + 18 = 345618, a Thursday (day 4).
- GPS seconds: 2399 × 604,800 + 345,618 = 1451260818.
- 10-bit week: 2399 − 2 × 1024 = 351, after 2 rollovers.
Tips
- Many receivers report seconds of week with decimals; you can type them, for example
2399 345618.25.
- Some logs use GPS seconds counted from another epoch, or TAI, which is 19 seconds ahead of GPS time. Check your file’s documentation.
- If a device shows a date about 19.6 years in the past, it is probably reading the 10-bit week without the rollover.
Frequently asked questions
What is GPS time?
A continuous count of seconds that started at 00:00:00 UTC on 6 January 1980. Unlike UTC it has no leap seconds, so it runs ahead of UTC by the number of leap seconds added since then: 18 seconds since 1 January 2017.
What are the GPS week and seconds of week?
The week is the number of whole weeks since the start of GPS time; the seconds of week (time of week, TOW) count from 00:00:00 GPS time on Sunday, from 0 to 604,799. GPS seconds = week × 604,800 + seconds of week.
What is the GPS week rollover?
The original navigation message carries the week in 10 bits, so it counts 0 to 1023 and starts again. That happened in August 1999 and April 2019. The converter shows the full week, the 10-bit week and how many rollovers have passed.
Does the tool know about future leap seconds?
Its table runs to the leap second at the end of 2016. If a new one is ever announced, results after it would be one second off until the table is updated.
How do I enter a local time?
Convert it to UTC first, for example with the time zone converter; this tool reads the date and time you type as UTC.