There are two separate interpretations of your question, due to English, not to your question-writing skills. In (America) English, "bad day" can be interpreted to mean being in a bad mood, having bad luck, or both.
For having a bad mood, John Feltz's answer of 'getting up on the wrong side of the bed' is spot-on and usable in almost any situation.
I'll add a more colloquial and cruder alternative:
"Who peed in your Cheerios?"
You can substitute almost any common breakfast cereal for Cheerios while keeping the exact same meaning (Fruit Loops, for example), although I (and the Urban Dictionary) agree that Cheerios is the most common. I've heard some unsubstantiated rumors that Canadians say "Who pooped in your poutine?"
If you're talking about the concept of just having a day of bad luck, English has at least one specific option:
What gypsy did you piss off?
The superstition behind this is that gypsy beggars will curse people who don't give them money or don't help them.