What's the drift like on a G Shock with no time signal available? There isn't a time signal in my region.

I've been considering getting a second watch (on top of my Coros running watch) because my phone has bad time drift when in battery saver + airplane mode, and my watch has a habit of dying at the wrong moment because of GPS and sleep tracking power drain.

That doesn't sound like it would be a problem, but I am in the habit of 5+ day hikes with no cell service and the occasional 40 hour flight with 3 layovers each in a different time zone.