What is the GPS epoch?

The GPS epoch is January 6, 1980, 00:00:00 UTC. All GPS week numbers and seconds are counted from this point.

What is GPS week rollover?

GPS week numbers are stored in a 10-bit field, so they reset to 0 every 1024 weeks (~19.7 years). The first rollover was August 21, 1999; the second was April 6, 2019. This tool uses the full 13-bit extended week number, so it handles rollovers correctly as long as you provide the correct week number.

Why does GPS time differ from UTC?

UTC inserts leap seconds to stay aligned with Earth's rotation. GPS time does not use leap seconds, so it runs ahead of UTC. As of 2024, GPS time is 18 seconds ahead of UTC.

What is "seconds of week"?

Seconds of week (SOW) counts elapsed seconds from the start of the current GPS week (Sunday 00:00:00 GPS time). It ranges from 0 to 604799 (7 days × 24 h × 3600 s − 1).

How accurate is this converter?

The converter uses the complete IERS leap second table through 2017 (the most recent addition). It is accurate to the second for any date within the GPS era. Sub-second precision is supported via fractional seconds input.

What is the difference between GPS time and GLONASS/Galileo time?

Each GNSS uses its own epoch and leap second policy. GPS time starts Jan 6, 1980. Galileo System Time (GST) also starts the same epoch but was defined separately. GLONASS uses UTC+3 Moscow time with leap seconds. This tool specifically handles GPS time.

GPS Time Converter

Name: GPS Time Converter
Availability: InStock
Author: Nham Vu

Convert GPS week number and seconds-of-week to UTC date/time, or enter a UTC date to get the GPS time equivalent.

GPS Time to UTC

Enter a GPS week number and seconds of week.

GPS Week Number

Seconds of Week

Range: 0 – 604799 (fractional seconds allowed)

UTC to GPS Time

Enter a UTC date and time to get the GPS equivalent.

UTC Date/Time

Must be on or after January 6, 1980

Fractional Seconds (optional)

GPS Leap Second Reference

GPS time does not use leap seconds. The table below shows when UTC leap seconds were inserted and the cumulative GPS–UTC offset at each point.

Date (UTC)	GPS Week	GPS Ahead of UTC (s)

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Summary

Convert GPS week number and seconds-of-week to UTC date/time, or enter a UTC date to get the GPS time equivalent.

How it works

GPS time began at the GPS epoch: January 6, 1980, 00:00:00 UTC.
Time is expressed as a GPS week number (rolling over every 1024 weeks) and seconds of week (0 to 604799).
To convert GPS to UTC: compute total seconds since GPS epoch, then subtract the applicable leap second count.
Leap seconds are added to UTC periodically; the converter uses the complete IERS leap second table.
Enter GPS week + seconds or a UTC date/time and click Convert — results appear instantly.

Use cases

Decoding GNSS receiver logs that output raw GPS timestamps.
Cross-checking GPS satellite signal timestamps against UTC.
Aviation and surveying applications requiring precise time synchronization.
Validating GPS data in scientific datasets or telemetry streams.
Converting navigation file headers (RINEX format) between time scales.
Educational use when studying the GPS coordinate and timing system.

Frequently Asked Questions

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Last updated: 2026-05-28 · Reviewed by Nham Vu