Durations and Turns

[Cheesegear]

Maybe I can't read good...

It's an extremely rare case that a combat will last 10 or more rounds. ...But let's say one did. So far, so good.

Many spells have a duration of a 1 minute (10 rounds). Cool.

You're in combat. It's grueling, it's bad. You've managed to hold Concentration the entire time somehow - your dice are on fire. It comes back around to your turn...

Does the spell end at the start of your turn, or at the end?

[Ignimortis]

I don't think there's a clear rule, buuuut...

If you cast the spell on your turn, it has been active on your turn, and then on 9 more turns, so it would expire at the start of your 10th turn after casting the spell, since that would be the 11th turn the spell would've been active.

[Mastikator]

I concur with Ignimortis. It ends at the start of your 10th turn.

If you somehow manage to cast it off your turn then I'd go with at the end of your turn.

[Segev]

Yeah, "You get ten of your turns during which a minute-long duration spell is active," seems like a good guideline.

[EggKookoo]

If you want a visualization, find 10 tokens or like poker chips. When you cast the spell, stack the tokens. At the start of each subsequent turn, remove a token. The spell ends the moment you remove the last token.

[Oramac]

I don't think there's a clear rule, buuuut...

If you cast the spell on your turn, it has been active on your turn, and then on 9 more turns, so it would expire at the start of your 10th turn after casting the spell, since that would be the 11th turn the spell would've been active.

I agree.

That being said, as a DM I would most likely allow it to last until the end of your turn in the 10th round, simply for the "fun factor". Especially if the combat is so grueling that it's lasted the full 10 rounds, you probably need that extra round pretty badly.

[Reach Weapon]

If you cast the spell on your turn, it has been active on your turn [...]

I'd argue that ignores casting time, which (much less so for bonus action spells at the beginning of your turn) takes up a significant portion of the time your turn comprises, and therefore the correct rounding is to the end of your 10th complete turn.

To put it another way, any effect during your casting turn happens at T minus 0 rounds, so you still have 10 rounds of duration remaining.

[Samayu]

If it had a duration of one round, you'd assume it ended at the end of your next turn. Otherwise it would end before you had an action to take advantage of whatever effect it had.

So I'd say a duration of ten round means the round you cast it in plus nine more, and it lasts through the end of that last turn.

[PhoenixPhyre]

I don't think there's a clear rule, buuuut...

If you cast the spell on your turn, it has been active on your turn, and then on 9 more turns, so it would expire at the start of your 10th turn after casting the spell, since that would be the 11th turn the spell would've been active.

I concur with this as a general operating principle.

[Psyren]

If it had a duration of one round, you'd assume it ended at the end of your next turn. Otherwise it would end before you had an action to take advantage of whatever effect it had.

So I'd say a duration of ten round means the round you cast it in plus nine more, and it lasts through the end of that last turn.

^ Yeah that. If it was the beginning of your next turn rather than the end, then True Strike becomes even more useless than it already is. So a 1 minute spell ends at the end of turn 10.

[Reach Weapon]

If it had a duration of one round, you'd assume it ended at the end of your next turn.

That reads like another argument in favor of starting the "stopwatch" at 0, and then counting out 10 rounds, as I advocated above.

[...] therefore the correct rounding is to the end of your 10th complete turn.

[KorvinStarmast]

To put it another way, any effect during your casting turn happens at T minus 0 rounds, so you still have 10 rounds of duration remaining.

I tend to do it that way. I can count on two hands the number of fights we have had that lasted 10 rounds. But we have had some.

^ Yeah that. If it was the beginning of your next turn rather than the end, then True Strike becomes even more useless than it already is. So a 1 minute spell ends at the end of turn 10.

Concur.