GPS week and seconds to UTC
The time for a week and seconds of week, including 10-bit weeks with their rollover era.
IERS Bulletin C (leap seconds) Bulletin C 72 runs out on 2027-06-30. Sources
That is 2026-09-18T00:00:00Z.
- GPS week
- GPS − UTC
Provenance
- Computed by
- time.scale.gps-to-utc 1.0.0, core 0.1.0
- Model
- UTC = GPS time − (TAI − UTC − 19 s); full week = 10-bit week + 1,024 × era
- Accuracy
- Exact for dates the leap-second table covers; instants inside a leap second print as 23:59:60
- Reference data
- version IERS Bulletin C 72 (2026-07-06) of a reference dataset
- Notes
- None
- Cites
- U.S. Space Force, Space Systems Command, IS-GPS-200N, NAVSTAR GPS Space Segment/Navigation User Segment Interfaces; International Earth Rotation and Reference Systems Service, IERS Bulletin C 72
Something look off?
How we got thisFormula, worked example, sources, and proof
Model: UTC = GPS time − (TAI − UTC − 19 s); full week = 10-bit week + 1,024 × era
Accuracy: Exact for dates the leap-second table covers; instants inside a leap second print as 23:59:60
When to use this: Use this to turn a GPS week and seconds of week back into a UTC instant: a timestamp out of a RINEX file, an almanac, a receiver log or a navigation message. Give a full week on its own, or a 10-bit week together with the era it came from.
Limitations: A week below 1,024 is ambiguous -- it could be a 10-bit week from 1980, 1999 or 2019 -- and is refused without an era rather than guessed at; a full week of 1,024 or more is refused *with* one, since that would double-count. GPS − UTC comes from a published leap-second table, so an instant past the embedded table's expiry could move by a second, and the result says so. An instant inside an inserted leap second prints as 23:59:60, which is a real UTC time and not an overflow.
Worked example: Week 2436, second 432018. Source: Inverse of the add-practitioner-essentials GPS week scenario. It is golden test vector v001, and every build checks the tool still gives its answer within its tolerance.
You enter
- Seconds of week
- 432018
- GPS week
- 2436
You get
- UTC
- 2026-09-18T00:00:00Z
- GPS week
- 2436
- GPS − UTC
- 18 s
Review: Not yet independently reviewed by a geodesist.
Last verified: 2026-09-18, when a maintainer last confirmed this tool's sources at the issuer. See the sources ledger.
Status: version 1.0.0, core 0.1.0. See this tool in the verification report.
Checked against: 22 golden test vectors (download the test vectors, each with its source and tolerance). See how results are checked and every source.
Sources
- IS-GPS-200N, NAVSTAR GPS Space Segment/Navigation User Segment Interfaces, U.S. Space Force, Space Systems Command, Revision N. Sections 3.3.4 (GPS time, epoch 1980 January 6) and 20.3.3.3.1.1 (10-bit transmission week number). Read free.
- IERS Bulletin C 72, International Earth Rotation and Reference Systems Service, Paris, 6 July 2026. UTC − TAI = −37 s from 2017 January 1 until further notice; no leap second at the end of December 2026. Read free.
Terms
- GPS: Global Positioning System
- The US satellite navigation system. Its time scale runs a fixed number of seconds ahead of UTC (18 s since 2017) because it never adds leap seconds. Source: IS-GPS-200 GPS interface specification
- UTC: Coordinated Universal Time
- The world's civil time standard, kept within 0.9 s of Earth's rotation by leap seconds. Aviation calls it Zulu time, written with a Z. Source: IERS Bulletin C (leap seconds)
GPS — Global Positioning System
The US satellite navigation system. Its time scale runs a fixed number of seconds ahead of UTC (18 s since 2017) because it never adds leap seconds.
Source: IS-GPS-200 GPS interface specification
UTC — Coordinated Universal Time
The world's civil time standard, kept within 0.9 s of Earth's rotation by leap seconds. Aviation calls it Zulu time, written with a Z.
Source: IERS Bulletin C (leap seconds)