This app calculates the Equal Time Point (ETP) — the position along your route where the time to continue to your destination equals the time to return to your departure or alternate airfield. The ETP is determined based on True Airspeed (TAS), wind direction and velocity, track, and the total distance between the two points for which you want to calculate the ETP. The result includes both the ETP distance and ETP time, measured from the point of departure.

Functional Demo: https://www.theairlinepilots.com/apps/etp.php