A discharged CMOS battery often causes a system to lose track of time and date settings when powered off, as this battery powers the real-time clock. The BIOS settings, including time and date, revert when this battery fails. Option A (time server misconfiguration) would impact multiple devices. BIOS updates (Option B) and CPU performance (Option D) are unrelated to timekeeping issues, as outlined in CompTIA A+ Core 1 (220-1101) exam objectives under hardware troubleshooting.