Users of GPS units will have the opportunity to weather a special GPS-only Y2K-type storm several months prior to New Year’s Eve. Since the Global Positioning System counts time from midnight, Jan. 6, 1980, and the rollover time was slated for 1,024 weeks from that date, the new GPS millennium will actually begin at midnight, Aug. 21, 1999, for GPS units.
Furthermore, GPS time is 13 seconds ahead of Coordinated Universal Time (UTC) since UTC accounts for leap seconds and GPS does not. So the rollover will actually occur at 23:59:47 UTC on August 21.
Most GPS units will be unaffected, according to industry reports, except for certain lower-end models purchased prior to roughly 1993. If you have an older GPS, you might want to contact the manufacturer to see if your unit will be affected by the week rollover issue.