Is a spell's duration tied to its effect, or the time experienced by its caster?

Question

Is a spell's duration tied to its effect, or the time experienced by its caster?

Alternative wording: With regard's to time dilation effects being in play, does a spell's effect last for its designated period from it's own perspective or from it's caster's point of view?

Consider Time Stop and summoning an ally during this spell. Does that ally's duration start counting once Time Stop's effect ends? Or does it start counting down the moment it is summoned, minus any "extra rounds" you used within the effect of Time Stop?

Alternative scenario:

With regards to Harrowed Home (emphasis mine):

As long as you are not in your harrowed home, time ceases to pass for anything and anyone still in your pocket dimension; creatures cannot move, objects do not decay, and everything remains exactly the same as you left it the last time you visited the plane. Time continues as normal whenever you are inside your harrowed home.

Were you to leave a summoned ally inside, would they expire counting on your rounds outside the realm or their own rounds, since they are their own creature and have 'rounds remaining' which is essentially "paused" in your absence from that realm.

If they expire after 'existing outside their native realms for X rounds' that would suggest you can cast dozens of summon monsters and direct them inside the portal (costing you a single round of their existence) where at a later date you can create a new portal and have the dozens (probably more) of summoned creatures pour out of the portal and do battle for you.

Answer 1

I would say that the duration counts the time experienced by the subject. That is, if your summoned creature cast time stop itself,¹ then the time stop time should count against the summoning’s duration. Likewise, if you cast some buff spell on yourself, and then cast time stop (or cast a buff on yourself during time stop), then the time in the time stop would count against the duration. But for everything outside of the subject of time stop, time doesn’t move (in a measurable way), and it shouldn’t count for the duration.

A summoned creature is a separate creature, regardless of when it was summoned. It never benefits from your time stop, so even if you summoned it during time stop it immediately freezes and time does not advance for it. The remaining rounds of time stop do not count against its duration.

So yes, your scenario with harrowed home would work—which is precisely why I doubt I’d allow harrowed home at all. It’s never come up in a game I’ve been in, as GM or player, but I’m very familiar with all the powerful shenanigans that one can get up to with quintessence, a psionic power from 3.5e that stops time for those immersed in it—and quintessence is a very inconvenient form of stopping time (you only produce an ounce at a time, and once you have more than a pound of the stuff, using psionics around it gets harder). I allow quintessence, but mostly because it’s too awkward to practically abuse; harrowed home, on the other hand, just seems too easy and too likely to cause problems.

That, and because I consider the harrow deck one of the absolute dumbest things in Pathfinder. Not a healthy addition to the game at all, in my view.

1. _{With Use Magic Device on a scroll of time stop, I suppose, since there is not and never should be a summonable spellcaster, much less one with access to 9th-level spells.}