There’s a toggle in the settings and quick settings that brings system-wide dark mode.
It is the update to the vivo Y12 which was launched in 2019. Vivo Y12 PD1901BF Firmware (Stock ROM) The Vivo Firmware helps you Upgrade or Downgrade the Stock Firmware (OS) of your Vivo Smartphone, FeaturePhone, and Tablet. Touch and hold any empty section of a Home screen. In this Step, Choose option Erase all Data.
3 To Disable Date & Time page in Settings.
On the popup that appears, tap on 30 minutes or choose the longest available option.