When is the 3G sunsetting happening?

Carriers have already begun shutting down the network in certain areas.  3G may already be phased-out in your area.  While there may be delays and shifts, the network will be gone by the end of the year.  Here's a schedule of when the networks plan to complete their 3G phase-out:
AT&T: February 1, 2022
Sprint: March 31, 2022
T-Mobile: July 1, 2022
Verizon: December 31, 2022
Carriers such as Cricket, Boost and Straight Talk utilize these networks, so if you don't see your network listed, you could still be affected.