Probability = desired outcomes / possible ones
You are asking on one day out of 365, so I would say
It's just a small detail but a very important one.
For example, it's true for a (perfect) dice: chance on throwing 6 is desired/possible = 1/6.
But let's take the lottery: chance on winning? Possible outcomes: yes and no, so 2. Chance: 1/2. I hope so, but I don't think so