How to Fix Date and Time Resetting on the Miyoo Mini Plus

Causes

• Depleted real-time-clock (RTC) backup cell — the Miyoo Mini Plus keeps the date and time with an RTC that runs on a small backup power source. If the unit is left uncharged for a long stretch, or the backup cell was never charged in the first place, the clock loses all state the moment the device is powered off and resets to a default time on every boot.
• Firmware bugs corrupting the RTC state — community reports on the Miyoo (OnionOS issue trackers) show the clock drifting or stopping entirely after a reinstall or after a network/WiFi change, even when the device stays powered. The time can be off by several minutes or reset completely until it is manually corrected.
• No time source when the device is off — the Miyoo Mini Plus does not keep NTP-synced time across a full power-off unless the RTC backup is healthy. If it is powered down completely with no WiFi sync available, the clock only reflects whatever the RTC cell can hold on its own.
• Partial or interrupted update/reinstall — a botched OnionOS update can leave the clock-control files half-written, so the stored time is never read back correctly and the date resets to the firmware default after a reboot.
• RTC cell never charging because the device is rarely on a charger — the backup cell is (re)charged from the main battery while the device runs or charges. A unit that is only ever powered on briefly may never top the RTC cell up, leaving it permanently too weak to hold the time.

How to Fix

1. Set the clock manually and let the RTC cell charge — go to Settings → Clock / Date & Time and set the correct date and time, then leave the Miyoo Mini Plus powered on and connected to a charger for a few hours. This gives the backup cell a chance to recharge so it can hold the time while the device is off.
2. Enable WiFi time sync (NTP) — connect the device to your network and turn on automatic time sync in OnionOS's network/time settings. When the clock drifts, reconnect to WiFi and the device re-syncs to the correct time instead of staying wrong.
3. Keep the device powered or avoid long fully-off stretches — while the backup cell is weak, prefer putting the Miyoo Mini Plus into its sleep/standby state rather than a full power-off, and avoid leaving it completely dead for weeks. A trickle of power on the board keeps the RTC running.
4. Update OnionOS to the latest version — release notes and issue reports show RTC and clock-reset bugs fixed in newer OnionOS builds. Update the firmware from the main menu (or reinstall the latest release on a quality card), then re-sync the clock.
5. Reinstall OnionOS cleanly if the bug persists — back up your Saves and BIOS folders, format the card to FAT32, and do a fresh OnionOS install. Corrupted clock-control state left over from a botched update is cleared by a clean install.
6. Replace the RTC backup cell if it still will not hold time — if the clock resets every single power-off even after charging and a clean install, the backup cell itself has failed. Replace it with a compatible RTC battery/coin cell for the Miyoo Mini Plus (available from retro-handheld parts shops), following the board layout, or have the swap done if you are not comfortable opening the device.