The US DoD GPS system provides essential positioning and timing information to many applications in daily use and aviation including FLARM. As part of the GPS design, the time is encoded in a format which restarts at zero every 1024 weeks (or merely 20 years), next time in the evening of April 6, 2019.
This is currently widely discussed on the aviation community, EASA today has published a Safety Information Bulletin.
The manufacturer of the GPS receiver modules used in all of your end-user products has confirmed to us already in May 2018 that these “modules have been tested and can handle the year 2019 GPS week number rollover without issue”.