# Calculating shabbat candle lighting time

Is it possible to calculate the candle lighting time based on location and date alone?

Assume all you have is a GPS, a watch and a calculator.

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Mordechai Ben Daniel, Welcome to mi.yodeya, and thanks very much for the interesting question! I look forward to seeing you around. – Isaac Moses Dec 1 '10 at 20:08
Keep in mind that one is not allowed to start Shabos at a later time than the community's latest starting time. So if you "prove" that candle lighting should be 3 minutes later than the time that the community lights, you still can not start Shabos later than when the community does if you proof is not accepted. But if you are on the road or stuck in an airport outside of a city, start calculating - You may even want to use Rabeinu Tam time :-) – inSeattle Dec 6 '10 at 4:03
Also can Be done With myzmanim.com – SimchasTorah Dec 6 '10 at 4:04
Although that's going to be at the end of kabbolas shabbos/borchu which is usually after that time. – YDK Dec 6 '10 at 7:44

Theoretically yes (assuming candle lighting is just 18 minutes less than sunset), as here's the formula for sunset time based on date, latitude, and longitude; but it's a doozy!

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Interesting that no one adjusts the 18 minutes. – YDK Dec 1 '10 at 21:43
what about altitude? – Sam Dec 2 '10 at 2:14
@YDK - adjust it for what? IIUC, the 18 minutes are a sort of buffer zone to ensure that Shabbos won't be violated. That doesn't change depending on where a person is located. – Dave Dec 2 '10 at 3:47
@Sam - Unless you're way above sea level, like in an airplane, altitude won't have a significant effect on the time of sunset. A more complicated question is how to deal with mountainous terrain; see this link for a comprehensive discussion about it: chaitables.com/chaiintro.html – Dave Dec 2 '10 at 4:25
@Dave , sunset in the Washington Heights is considerably later than in the Lower East End of Manhattan in the summer time. The full sun can still be seen in the Heights when the official time for sunset has occured for the Lower East End. (I asked a couple of poseks about that and was told to pretend I didn't ask) – inSeattle Dec 8 '10 at 5:18

I believe the common custom is indeed calculated based on latitude and longitude alone. However, this is certainly not a unanimous assumption, considering that in addition to latitude and longitude, your own elevation, as well as the elevation of the western horizon, will affect the appearance of sunset. I believe Yeshivat Birkat Moshe, in Maale Adumim, under the auspices of Rav Nachum Rabinovitch, shelita"h, accepts Shabbat well before the sea-level calculations of the popular sunset tables.

See Shabbath 118b:

א"ר יוסי יהא חלקי ממכניסי שבת בטבריא וממוציאי שבת בצפורי

Said Rabbi Yosi: Let my lot be of those who enter the Sabbath in Tiberia (lower elevation = earlier time; see Rashi ad loc) and of those who leave Sabbath in Zippori (higher elevation = later time).

See also here and here, as well as Shu"t Siach Nachum Responsum 17, p. 40.

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