Caffeine in the afternoon is always a bad idea. Always. "Afternoon" literally means "any time after noon." And that's when you shouldn't drink caffeine. Or else you will be awake until 2:30 in the morning, asking yourself just why you needed that caffeine so badly in the first place.
Sub-note to note to self:
This is Note to Self #346 regarding this exact same thing. Get a clue.