P.3.1- At the beginning of each phase or step, any triggered abilities (see Rule A.4) that trigger "at the beginning of" that phase or step are added to the stack. [CompRules 1999/04/23]
P.3.2- Once triggered abilities are placed on the stack, the current player receives priority, and play continues until all players pass while the stack is empty. See Rule T.2 for details. [CompRules 1999/04/23]
P.3.3- When a phase or step ends, all effects scheduled to last "until the end of" that phase or step end. [CompRules 1999/04/23]
P.3.4- When a phase or step begins, all effects scheduled to last "until" the current phase or step end. For example, an effect that lasts "until your next upkeep step" will end at the beginning of your upkeep step before checking for triggered abilities. [CompRules 1999/11/01]
P.3.5- When a phase ends (but not a step), any unused mana in each player's mana pool is lost, and that player loses 1 life for each point of mana lost this way. This is called "mana burn" (see Rule G.22). [CompRules 1999/04/23] Any abilities triggering on this loss of life wait until the next phase or step where a player receives priority before they are played. [D'Angelo 1999/05/01] Checking if a player loses the game from having zero or less life waits until the next phase or step where a player receives priority. [DeLaney 2000/01/13]
P.3.6- No game event ever takes place between phases, between steps, or between turns. [CompRules 1999/04/23]
P.3.7- A phase or step ends when both players pass while the stack (see Rule T.2) is empty. [CompRules 1999/04/23]
P.3.Ruling.1- If a phase or step is skipped, any effects that last "until" that phase or step continue. For example, if your draw step is skipped, any effect lasting until your next draw step would not end at that time. [D'Angelo 1999/05/01]