And also so that the power required for the display may be redirected to the more critical timekeeping function if necessary. If you only have enough power lef

And also so that the power required for the display may be redirected to the more critical timekeeping function if necessary. If you only have enough power left to keep time for the next month or to power the display for the next day, you turn the display off and hope that more power is added to the system during that month.