The GPS week number is given in the GPS legacy navigation (LNAV) message of 10 bits. Hence, every 1,024 weeks (almost 20 years) it jumps from 1,024 back to zero.
This roll-over will occur 18 seconds before the 0000 UTC boundary between 6 and 7 April. The 18s represents the current difference between GPS time and UTC.
GPS weeks started on 6 January 1980, and the first roll-over was on 21/22 August 1999. During that roll-over, many receivers became confused and stopped working. It is hoped that such problems will not occur again, but suppliers and operators are aware of the possibility, and some manufacturers have provided software updates and guidance for legacy receivers.
It should be noted that modern civil navigation (CNAV) GPS and other GNSS signals all use a 13-bit week number - their first roll-over will occur on 5/6 January 2137.
Anyone finding that their GPS receiver stops working after midnight on 6 April should contact the manufactures.