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).
May 3, 2019 · War of the Spark
When a phase or step ends, any effects scheduled to last “until end of” that phase or step expire. When a phase or step begins, any effects scheduled to last “until” that phase or step expire. 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. Effects that last “until end of turn” are subject to special rules; see rule 514.2.
January 25, 2019 · Ravnica Allegiance
When a phase or step ends, any effects scheduled to last "until end of" that phase or step expire. When a phase or step begins, any effects scheduled to last "until" that phase or step expire. 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. Effects that last "until end of turn" are subject to special rules; see rule 514.2.
May 1, 2014 · Journey into Nyx
When a phase or step ends, any effects scheduled to last “until end of” that phase or step expire. When a phase or step begins, any effects scheduled to last “until” that phase or step expire. 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. Effects that last “until end of turn” are subject to special rules; see rule 514.2.
September 30, 2011 · Innistrad
When a phase or step ends, any effects scheduled to last "until end of" that phase or step expire. When a phase or step begins, any effects scheduled to last "until" that phase or step expire. 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. Effects that last "until end of turn" are subject to special rules; see rule 514.2.
June 17, 2011 · Commander 2011
When a phase or step ends, any effects scheduled to last “until end of” that phase or step expire.
April 1, 2011 · Duel Decks: Knights vs. Dragons
When a phase or step ends, any effects scheduled to last "until end of" that phase or step expire. When a phase or step begins, any effects scheduled to last "until" that phase or step expire. 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. Effects that last "until end of turn" are subject to special rules; see rule 514.2.
February 4, 2011 · Mirrodin Besieged
When a phase or step ends, any effects scheduled to last “until end of” that phase or step expire. When a phase or step begins, any effects scheduled to last “until” that phase or step expire. 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. Effects that last “until end of turn” are subject to special rules; see rule 514.2.
October 1, 2010 · Scars of Mirrodin
When a phase or step ends, any effects scheduled to last “until end of” that phase or step expire.
February 1, 2010 · Worldwake
When a phase or step ends, any effects scheduled to last "until end of" that phase or step expire. When a phase or step begins, any effects scheduled to last "until" that phase or step expire. 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. Effects that last "until end of turn" are subject to special rules; see rule 514.2.