Can Jews standing naval watches take their shabbat in shifts?

Question

Suppose you have an major naval ship (aircraft carrier or nuclear sub) with a small complement of Jews on board. They're divided by the executive officer to stand watches, same as the rest of the crew, 6 hours each. Some of the Jews will stand different watches than others.

So Friday night happens aboard the ship. Assume sundown occurs during watch A. You're on duty, so you can't say the prayers. During this time watches B and C are awake but not yet on duty, so they probably can. Watch D is most likely asleep.

Do the Jews on the different watches have to rotate their individual clocks so they can observe when they go off-shift, as an extension of observing Shabbat in the desert, where each have to create their own individual time reference out of necessity?

The necessity is this: The Jew on A watch when the three stars normally appear cannot perform the observance because that would be dereliction of duty. So there's a necessity to rotate his clock to another time zone 6 hours hence where the three stars would appear as soon as he went off shift. Watches B and C have no necessity. However, the poor Jew on watch D needs rack time after a full day of work. He would need a 12 hour time zone difference! At least that's how I understand it? Maybe someone understands better.

Answer 1

One keeps the sabbath — abstains from certain activities and tries to engage in holy pursuits — from sundown Friday to nighttime Saturday, irrespective of his ability to perform the sabbath ceremonies. Such abstentions and pursuits may be subject to your commanding officers' restrictions on you; consult a rabbi for specific questions as they apply to you.

The ceremonies are done as usual. If that's impossible, the nighttime kidush can be done all night, or even by day; the havdala can be done all night, even the next day, or even later; and the prayer services can be done for various (fairly long) lengths of time, or made up for. Again, consult your rabbi for specific questions as they apply to you.

Answer 2

"Shifting one's personal clock" and the like -- the example you gave was someone who finds himself in the wilderness and has no sense of what day it is -- the Talmud says he should start some sort of calendar and work with it. That's not applicable to the situation at hand, in which everyone agrees that it's now Friday January 31st 2014 and that sunset is at 6pm (or whatnot). So that's when shabbat begins for everyone on the boat, no matter what they're up to.

If it's necessary for someone to stand watch, then they are obligated to do so -- protecting lives trumps any obligations of shabbat -- but it's still shabbat. This is basically the same as the doctor who gets called in to perform emergency surgery on shabbat -- it's still shabbat, but he is obligated to save a life even if that means driving, cutting, writing, whatever. As far as taking the shift to begin with, this has long been discussed (e.g. doctors' call schedules) and relates to the question of: "if a life-and-death situation arises, I violate shabbat. How hard must I try to avoid getting put into such a situation to begin with?" But let's assume that the shifts have already been assigned.

At that point the question is just "if I'm busy doing life-saving work and can't pray, what do I pray afterwards?". For instance, if someone's shift goes from 3pm to 11pm on Friday, sunset is sometime during that stretch, and he cannot recite any prayers while on shift, then he can simply do all the prayers and kiddush at 11pm. If he was occupied from sunset till dawn, then he should recite Shabbat morning prayers but repeat the amida to make up the missed one from last night, then recite the full Friday-night kiddush before eating breakfast on Saturday morning. Similarly, someone who was occupied from dawn till noon on Saturday should recite amida at Mincha twice, to make up for the missed prayer. Someone on shift 11am-7pm Saturday (let's assume sunset is 5pm) had missed Mincha (afternoon prayers), so he would do the Saturday-night prayers and recite its Amida twice, the second time making up for missing Saturday afternoon. (The exact same concept would hold if you couldn't pray on a Tuesday afternoon, for that matter.)