HTC One M8 for Windows - Manual (Page 195)

Installing an update
When you see the notification about an available software update, you can
update your phone right away. Or you can dismiss the notification and
update some other time. Your phone will remind you again in a few days.
Have you prepared your phone for the update? If you haven't,
please see
Preparing for a software update on page 194 on what
you should check and prepare.
Correcting the date and time
If you're having trouble installing a software update, your phone may not
have been set with the correct date and time. In most cases, the date and
time is set automatically. But if it's not, you can set it manually.
1. Swipe down from the top edge of the screen with one finger.
2. Tap All settings > date+time.
3. Turn off Set date and time automatically.
4. Set the correct time zone, date, and time.
Factory reset
A factory reset is not a step to be taken lightly. It’ll remove your primary
Microsoft account and you may lose data if it has not been synced. Be sure
to back up any data and files you want to keep before you do a factory
reset.
Update and reset 195