1. The date/time is stored in the BIOS.
2. Windows starts and gets the date/time from the BIOS.
3. If the time is incorrect, then change it from within Windows.
4. Windows modifies the BIOS time (so if you had Linux installed as well it would then be the correct time if it booted).
*Long story short, all you need to know is that if the time is incorrect in Windows then change it to the correct time.