What does it mean if a clock stops at midnight?

i don't know but mine does 3 or 4 times a month - i took it to change the battery but was told there was nothing wrong with the old battery but he changed it anyway ( no he didn't charge me as i know him ) - and it still stops only at midnight !! can't think logically why it isn't 23.55 or 1.05 - but it is always midnight !!