Editing Global Positioning System (section)

==== Format ====
{{further|GPS week number rollover}}
As opposed to the year, month, and day format of the [[Gregorian calendar]], the GPS date is expressed as a week number and a seconds-into-week number. The week number is transmitted as a ten-[[bit]] field in the C/A and P(Y) navigation messages, and so it becomes zero again every 1,024&nbsp;weeks (19.6&nbsp;years). GPS week zero started at 00:00:00&nbsp;UTC (00:00:19&nbsp;TAI) on January 6, 1980, and the week number became zero again for the first time at 23:59:47&nbsp;UTC on August 21, 1999 (00:00:19&nbsp;TAI on August 22, 1999). It happened the second time at 23:59:42&nbsp;UTC on April 6, 2019. To determine the current Gregorian date, a GPS receiver must be provided with the approximate date (to within 3,584&nbsp;days) to correctly translate the GPS date signal. To address this concern in the future the modernized GPS civil navigation (CNAV) message will use a 13-bit field that only repeats every 8,192&nbsp;weeks (157&nbsp;years), thus lasting until 2137 (157&nbsp;years after GPS week zero).