Oliver went through a phase like that, either created when we put him for a nap and refused point blank, then be super cranky from 5pm or he'd sleep a little and still wake up in a foul mood. Thankfully it was just a phase as we still persisted in putting him down for his nap as usual and he seemed to get back on track again within a few weeks.
Now we've cut them out altogether as he has school in the afternoons, but he has an earlier bed time and still sleep 13hrs at night.