I was wondering if one of the supplements has an answe rto the following questions:
At the northpole, sun duration would be 6 months, right?
If a character travels using ReCo teleport magic (say from Paris to Constantinople) after casting a sun spell (or using a parma), does the spell end when the sun sets in Paris or in Constantinople? What happens if it's still day in Paris, but night in Constantinople? Does the Parma go down?
Any magical scholar would tell you that anywhere that the sun doesn't set for 6 months is clearly a Regio, so all bets are off re "normal rules". The North Pole would be (the same as) a Faerie or Magical Regio - and the duration of D:Sun spells there is up to the SG/Troupe.
Undefined afaik, but easily done.
D:Sun is relative to the effect, so it all depends on when the Sun sets on the effect itself,
it's relative to the Caster of the effect (or the Item that cast it?),
it's relative to the location where the effect was cast, regardless of where the caster and/or effect later move.
I like this option as I think the "magic" should reflect the point in time when and where it was invoked, and also reflect the change in local conditions.
Aside - that might cause havoc for items with the Constant Use and 2/day use, where they might need three uses if the item teleports between sunsets. Nice side-effect too if a Magi was to try to chase the dawn to maintain an effect.
This is not how Constant works for items. This is how the cost of Constant is calculated for items. The actual functioning is that at the first sunrise/sunset once created it activates a single time, and then it simply remains active forever. This showed up in HP, I believe. I don't think it's stated explicitly, but when I thought a MuVi effect needed to be listed in the errata this was explained to me as the canon interpretation for Constant item effects.
The side-box on ArM p99 for Constant Effects in the Labs section points out that a D:Sun effect, with Constant and 2/uses won't "flicker" at sunrise or sunset, but I'm not sure how that could be seen as anything but a Sun effect that gets continued by the device.
If (for whatever reason) the Sun sets on the device too many time in a typical daylight period of time, why will the device still function? What was the ref and wording on the HP? (not arguing, just interested)
For a constant effect a single MuVi spell need only trigger once ever to affect its casting. That is the specific context. If the effect were cast each sunrise/sunset, the MuVi spell would need more uses per day than are actually required. It's in the necromancy section of HP.
It has been stated in several Ars official books (maybe pre-5th edition, though; away from books) that in northern areas Sun duration effects last much longer and that magi consider this 6-month Sun effect to be a clear possibility. It is left open ended since nobody has tried, but yes, it should be possible.
For the later it is relative to your saga as has been pointed out. I also like the idea of the effect ending when itself is affected by sunrise/sunset, so if you teleport from Paris to Constantinople and the sun has already set in Constantinople BAM! your parma goes down instantly. The funny thing would be to get an AC to Australia and teleport there instead: see if the rising sun there maintains your parma active. that is a suitable research piece for your saga (totally undefined in canon).
You don't have to go to the North Pole to address this issue. Consider a magus in Scotland. He's going to deal with this all the time. During the summer, a spell with duration Sun cast during the day will have a much longer duration than the same spell cast during the night. The reverse is true during the winter. The North Pole only brings this issue to the extreme. But throughout Mythic Europe, the length of time between sunset and sunrise is almost always different from the time between sunrise and sunset.
While I believe the idea of the length of the day changing as you travel north to south has been mentioned before in ArM there is at least one case where cannon suggests that the idea of time zones and sunrise sunset changing from east to west doesn't happen in Mythic Europe.
The idea that House Guernicus ended the Schism War by timing their ritual to go off at sunrise and catch all the Deidne's with their Parma's Down really only makes sense if you assume sunrise happens at the exact same time every where. Now my guess is that's probably a case of authorial oversight. And you can explain it away by throwing in a bunch of stuff that isn't really mentioned. Like maybe the Fenicle Ritual was only suposed to get most Deidne's and the majority of them where lined up along the same longitudinal position. And even though they where in a knock down drag out war with the rest of the order Deidne weren't waking at dawn to refresh their Parma's so there was probably a couple hours leeway anyway.
Also in another case of Authorial Oversight. I played in a saga where the covenant was built around a regio that opened up two three very distant locations in Mythic Europe, Scotland, Venice, and a Pilgrims Hostel somewhere near Jerusalem. Parts of the covenant where divided up between each local and travel between them was fairly casual. Enough so that it justified a Living Conditions Bonus. "Aw the summer in the Holy Land a bit to hot for you go take a dip in a stream in Scotland". It was still several sessions into Saga before anyone realized that we hadn't even considered time zones.
There is no Daylight Savings in Europe. That is an American thing and not followed uniformly either.
Time "zones", per se, are an anachronism. There was little need to sync watches between two locations. But people are aware that the earth is curved, that the sun rises in the east and sets in the west, they understand as it begins to get bright in one area it is yet dark far to the west, and so on. There were not many timepieces, but they did exist in various forms. Though they would be calibrated to the sun, or a sun dial, so what you would have in effect was many multiple "micro-time zones". Scholars and magi would have an understanding of such things.
Yeah I know times zones are a modern thing. But I couldn't really think of a better way of summing up the principle.
Personally for ease of storytelling I'd be tempted to say that local time doesn't vary by longitude. The high latitude, land of the midnight sun, 30 days of night thing is cool color so Id use that if it comes up. But it gets confusing and complicated for very little payoff to worry about the time difference between Dublin and Crete.
The thing in house Guernicus is an oversight IMO. That chapter is one of the least fortunate examples of Canon changes, so I would not base myself on it to present a case. Quite funny, being the legal chapter et al.