Do you pay attention when daylight savings time begins/ends in different countries where you are running offers especially when using day parting?
I had my day parting set up using USA eastern time since this is where i am and this is what traffic source was using. But after time change i was getting weird results and when i looked into it i realized that the country where i was running had different daylight savings time schedule than US.
https://en.wikipedia.org/wiki/Daylig...ime_by_country