One of the more complex halachik problems in the modern world of globe-trotting (which will hopefully be possible again soon), is the question of how to count the days of the week, including shabbat, while changing time zones.

Due to the circular nature of the world, it was decided in relatively modern times by the nations of the world to fix a date line 180 degrees east of Greenwich, England , given that at the time , the British Empire was the centre of the world politically and logistically .

This avoids the problem of continually losing an hour as one moves east while gaining one as one moves west, to the point that two people travelling to a point from 2 different directions on the circular world would meet each other on 2 different days respectively .

If that were the case,  the same day and place could then be Thursday for the person who travelled west from England to say, Japan, and Friday for one who travelled  Eastwards, which would be unmanageable , to put it mildly.

Not to mention the issues each country would have in choosing whether its Thursday or Friday!

Once a dateline is set, when its midnight beginning of Friday on the Western side of the dateline , somewhere in the Pacific, its only midnight beginning Thursday on the other side, and a day is jumped as you cross the line, but at least everywhere else has a fixed date.

However, it is nothing more than a fictional line which theoretically could have been placed anywhere – it was placed in the middle of the Pacific intentionally to avoid the inconvenience of people on the  land  border changing days as they cross all the time , and in order to avoid islands along the 180 degree lines, the line was actually moved in certain places!

In fact, At least one island nation in the Pacific has actually switched before from one side to the other, for economically and logistically convenient factors!

When it comes to Shabbat, chagim, and other halachik  questions, we are faced with a major riddle – on the one hand, if the Torah does not recognise the concept of a dateline , than the day Shabbos falls will depend on which direction each jew reached a different time zone from, and for one Jew in a certain time zone, it could be Sunday, and for a different one, still shabbos .

Due to the absurdity of such a situation, most Poskim have recognised the fact that having a halachik dateline must be built into the halachik system, and some have even found hints at it in talmudic and medieval sources.

The problem is that assuming that we recognise the concept of a dateline, the fact that the British and their subjects decided with other countries to place the baseline at Greenwich and the dateline 180 degrees in either direction from it, with a few deviations, does not necessarily give this arbitrary dateline halachik weight.

The halachik dateline could thus be in a totally different place than the accepted international dateline , which would mean that some people would actually need to keep shabbos on Friday or Sunday according to the local calendar .

This would be inconvenient, but for something as weighty as shabbos, convenience is unlikely to be a factor – after all, unlike the chagim which are dependent on the date of the month , which in turn is dependent on the day that we declare Rosh Chinese ( in the past based on the new moon sightings and now on the calendar), shabbos is fixed from the 7 days of creations by tradition and can never change .

In addition, the days of the month and yom tov could only be changed with the official process of עבור declaring a leap year or leap month, a complex process which required a qualified court, as well as being in Israel in most cases – it could not simply be done based on what the local government recognizes as the correct day or date.

In fact, the most obvious place to set the baseline is where the Torah considers to be the centre of the world, namely Jerusalem, which would put the dateline far to the East of the international date line, if we follow the 180 degree system .

This is where some Poskim, including Rav Yechiel Michel Tucazinsky zt’l, leading poseik of Jerusalem in the mid twentieth century למנינם, put the dateline – he actually wrote an entire book on the subject!

According to this , Australia , New Zealand, and Japan keep shabbos the same time as the locals, being on our side of the dateline, but people in Hawaii, on the other side, do not, and would need to keep shabbos on the local Friday .

The problem is that some Poskim, such as the Chazon Ish, based on the Baal haMaor’s explanation of a cryptic Gemara in Rosh Hashana  ( maybe a future post when we get there ), hold that the dateline should be only 90 degrees East of Jerusalem, putting at least most of Australia on our side of the line, but New Zealand and Japan on the other side .( the Chazon Ish applies a rule called גרירה whereby a continent or island is never split and follows the time zone that most of it is in , saving Australians at lot of hassle- interestingly the late Rav of Netanya, Rav David Shlush  zt’l, and great poseik in his own right, in his own lengthy work on the subject, disagrees and holds that a body of land may indeed be split in two.)

That would mean that New Zealand and Japan would be on the other side of the line and need to keep shabbos on Sunday!

Although many poskim come out that one may keep shabbos on the day the locals consider Saturday in both Hawai and New Zealand/Japan, many people are stringent and keep shabbos and chagim on both days, or at least refrain from biblically prohibited work on one of the two days in addition to keeping a full shabbos on the other .

Is this necessary, or just an unnecessary stringency, and what does it have to do with today’s daf (or not ?)

We are taught in a Beraita on this daf that one who is travelling through the desert and has lost track of the days of the week, should count 6 days from the time he realises this, and keep shabbos on the seventh .

This seems at first to indicate that if one is unsure when shabbos really should be, it is sufficient to follow one’s own 7 day cycle and keep one shabbos a week, even if it’s not on the accurate halachik day that others keep it on.

Although one could dispute this based on the well  known rules of chazal that  unlike yom tov, shabbos is fixed in stone and never changes based on people, as we discussed above , it seems at this stage of the sugya that so long as a person has his own fixed 7 day cycle, it’s OK to keep just one day as shabbos and treat the other days as regular days, seeing as he is unable to ascertain when the real shabbos is.

It could be argued that if this is the case, then even more so when an entire community is unsure of which day shabbos should be , given all the debates above, that it could be treated in a similar way and they could choose to follow the seven day cycle they have always followed locally , with visitors doing the same.

Of course, the comparison could be disputed, but the Gemara throws a major curveball at this in any case.

Rava rules that contrary to what we would think from a simple reading of the Beraita, this is not a blanket permit to do any forbidden work on the other 6 days .

Each of the 7 days is actually treated as if it could be shabbos, and most work is forbidden.

The only work that is permitted is that which is needed for his essential livelihood, which is considered pikuach nefesh (see Rashi who explicitly mentions this consideration)

Then in order to distinguish one day from the other in order that one shouldn’t forget about shabbos, the Gemora concludes that every 7 days, one should say Kiddush and Havdala, and that was the intention of the Beraita .

There is so much lomdus in the various movements in this piece, way out of the scope of this post, but it thus seems from the conclusion of the Gemara that this particular sugya would not be of major use in allowing  for our proposed leniency re the dateline .

One might thus indeed need to avoid at least biblically forbidden work on both days when in these regions that are subject to dispute!

Much more to say, but a nice way to whet one’s appetite for the subject , if it doesn’t give you too much of a headache- I find it makes me dizzy and I am certainly quite far from reaching a conclusion on my own on this issue.

Just to end with something from a current Gadol that I  have merited  to have some connection to-  I asked Rav Asher Weiss Shelita  in person once what he held regarding the dateline question.

His initial answer to me was that he holds that the ikar (most important argument ) is to do what the locals do.

I then pressed him a bit and asked if that means that he would himself do biblically prohibited melacha in New Zealand on the local Sunday – he smiled at me and send that he wasn’t sure!