Eight months and 10 days remain, as of March 21, before the FAA’s Automatic Dependent Surveillance-Broadcast Out mandate takes effect on Jan. 2, 2020. ADS-B uses satellites instead of ground-based radar to determine aircraft location, and is a key technology behind the FAA’s Next Generation Air Traffic Control System. The FAA has mandated ADS-B Out for flights after Jan. 1, 2020, in airspace where a transponder is required today.
Source: aopaFAA ADS-B mandate approaching quickly