MLB Service Time

An MLB regular season (AKA "championship season") must be at least 178 days but no more than 183 days in length, but 172 days constitutes a "full" MLB regular season for purposes of calculating MLB Service Time.
NOTE: Beginning in 2018, the MLB regular season will be extended to at least 182 days but no more than 187 days (186 days in 2019) so as to accommodate more off days during the course of the season.

1. A player cannot get credit for more than 172 days of MLB Service Time in any one MLB championship season (MLB regular season).

2. MLB Service Time is counted beginning on MLB Opening Day up through the last day of the MLB regular season (including any day a make-up game for a postponed game and/or a tie-breaker game is scheduled after the originally-scheduled conclusion of the MLB regular season).

3. MLB Service Time can only be accrued during the MLB championship season (MLB regular season). MLB Service Time cannot be accrued during the MLB post-season (Wild Card game, LDS, LCS, and World Series).

4. If an MLB regular season game or games are scheduled during Spring Training (prior to MLB Opening Day), only players on the MLB Active List or on an MLB Injured List or other MLB inactive list of the clubs participating in the games(s) accrue MLB Service Time. This would apply to any MLB regular season game(s) known as "international openers" that may be scheduled in Australia, Japan, Mexico, etc, during Spring Training and prior to MLB Opening Day. Otherwise, MLB Service Time cannot be accrued during Spring Training (prior to MLB Opening Day).

5. A player on an MLB Reserve List accrues a day of MLB Service Time for each day of the MLB regular season spent on an MLB Active List or on an MLB 7-day, 10-day, or 60-day Injured List (including days spent on a Minor League Injury Rehabilitation assignment), Paternity Leave List, Bereavement/Family Medical Emergency List, Suspended List, or Military List, or on the Restricted List as the result of a suspension for violation of the ban on the use of a prohibited substance or a suspension or leave of absence related to a violation or possible violation of the MLB domestic violence/child abuse policy.
EXCEPTION: Beginning in December 2016, a player suspended as the result of a violation of the ban on the use of prohibited substances will - NOT - receive credit for MLB Service Time while on the Restricted List unless it's the player's first or second positive test and the length of the suspension is subsequently reduced by at least 20 games by an arbitrator as the result of mitigating circumstances.

6. A player does not accrue MLB Service Time for days spent on the Disqualified List, Ineligible List, or Voluntary Retired List, or for days spent on the Restricted List for any reason other than a Prohibited Substance or Domestic Violence suspension.

7. A player traded during the MLB regular season continues to accrue MLB Service Time after being traded but before reporting to his new club.

8. A player who is Designated for Assignment (DFA) accrues MLB Service Time for the entire period of time he is Designated for Assignment during the MLB regular season, but if the player is Designated for Assignment prior to the start of the MLB regular season and the DFA period extends into the MLB regular season, the player does not accrue MLB Service Time while he is Designated for Assignment.

9. A player normally does not accrue MLB Service Time for days spent on Optional Assignment to the minor leagues. However, if a player spends less than 20 days on Optional Assignment to the minors during the course of a given MLB regular season, the player gets credit for MLB Service Time for the days spent on Optional Assignment.
EXCEPTION: If a player is optioned to the minors prior to accruing MLB Service Time that season (for example, if the player is optioned to the minors prior to MLB Opening Day) and then is released or sent outright to the minors prior to spending at least 20 days on Optional Assignment and then is not added to an MLB Active List (25-man roster) for the balance of that MLB regular season, the time spent on Optional Assignment prior to being released or outrighted does - NOT - count as MLB Service Time.

10. If a player spends at least 20 days on Optional Assignment to the minors in a given MLB regular season, the player does not accrue MLB Service Time for the days spent on Optional Assignment.
NOTE: Days spent on Optional Assignment during Spring Training (prior to MLB Opening Day) do not count toward the 20 days.

11. If a player is optioned to the minors, the player is not credited with a day of MLB Service Time for the day the player is optioned to the minors unless the player is optioned during or after the conclusion of an MLB regular season game played by his club that day. If a player is recalled from a minor league Optional Assignment, the player receives credit for a day of MLB Service Time beginning with the day the player is recalled.