Time needs vary widely for people. Some people need nanosecond precision. Probably most end-users wouldn't notice for quite a while if their system clock is off by literally years... I know I've done it before without noticing. However, the existence of the latter doesn't somehow invalidate the former... some people really do care quite deeply. If you are in the latter, it hardly much matters what you do. "Manually setting it off of my cell phone" or "ignoring it entirely" are mostly valid options.