The Daily Neutrino calculates every planet's position on your iPhone. Nothing is downloaded, and it works without a connection.
The calculations come from HDEngine, written by Kiryll Kulakowski, one of the two people who make The Daily Neutrino. It works out where each planet stands as seen from Earth, then which gate and line that position falls in.
Positions come from NASA JPL's DE440 ephemeris. Chiron's comes from JPL's Horizons system. The North and South Node are the Moon's true nodes.
The app carries the exact time of every gate and line change from 2020 to 2059, worked out in advance by the same engine. Notifications and widgets use these times.