Rule 500.5 · General
As a step or phase ends, if there are effects that last until the end of that step or phase, those effects expire. Then any unspent mana left in a player’s mana pool empties. This is a turn-based action that doesn’t use the stack (see rule 703.4q).
Subrules
Effects that last “until end of combat” expire at the end of the combat phase, not at the beginning of the end of combat step.