GPS Week Number Calculator

Why the rollover matters

Early GPS hardware only transmitted the week number as a 10-bit field, which rolls over every 1,024 weeks (about 19.6 years) — the first rollover happened in 1999, the second in 2019, and the third is due in late 2038. A receiver or logging system that hasn't been patched to handle this can miscalculate dates by exactly one 1,024-week cycle, silently producing a date roughly 19.6 years off. This calculator's "10-bit rollover" mode shows you what an unpatched receiver would report for a given real date.

Not to be confused with GPS time itself

GPS week number is a different representation from raw GPS time (seconds since the same 1980 epoch, ignoring leap seconds) — the Historical Epoch Converter handles that version. This tool is specifically for the week-and-day format used in NMEA/RINEX data and most GNSS receiver output.