My phone glitched last night and restarted itself, from the welcome screen I'd guess it's a Samsung D500.
When it was back up I checked the app and had to change the hour to 0 to match the phone, but after 11 hours it's 2 mins ahead again. My guess is that whatever it's comparing it's time to is not the part of the clock the user sets [that doesn't run fast or slow] but rather some other part entirely that keeps running fast so that the longer the phone is left turned on, the further ahead it will get.
Or at least that's my best guess.... I mean, it was minutes ahead but hours behind before the crash *shrugs*