Question: Is there anything halachically wrong with starting the Shabbat day meal in the afternoon?
Answer: We have already explained above regarding the laws of “the Mitzvah of enjoyment of Shabbat” that one is fully obligated to enjoy Shabbat through eating and drinking, as the verse in Yeshaya (Chapter 58) states, “And you shall call Shabbat [a day of] pleasure.” Thus, one may not fast on Shabbat, for by doing so, one is preventing himself from enjoying Shabbat.
The Sages tell us in the Gemara Masechet Pesachim (12b) that whoever does not taste anything until the sixth hour of the day (which is halachic midday) is considered to be “throwing a pebble into the flask” by eating from this point on. This means that it is not healthy at all to begin eating breakfast past midday. The Poskim therefore write that even on a regular weekday, one should not delay eating breakfast past six hours from the beginning of the morning. Maran Ha’Shulchan Aruch rules likewise in Chapter 157. We see clearly that one should not push off eating breakfast so much, even on a regular weekday; rather, one should be careful to eat before midday, meaning before six seasonal hours into the day.
The Talmud Yerushalmi quotes Rabbi Acha and Rabbi Avhu who said in the name of Rabbi Yose bar Chanina that one may not fast until the sixth hour of the day on Shabbat. The Rif and the Rosh (Chapter 1 of Masechet Shabbat) as well as the Tur and Maran Ha’Shulchan Aruch (Chapter 288) all rule likewise. Obviously, regarding all of these laws there is no distinction between men and women, for all are obligated in the Mitzvah of enjoying Shabbat.
Based on this, the Turei Zahav writes that communities that would customarily fast on Shabbat until midday in order to nullify certain harsh decrees that were decreed upon them are acting incorrectly, for by doing so, they are also nullifying the enjoyment of Shabbat.
However, if one knows beforehand that for whatever reason, one will not be able to eat before midday on Shabbat, one should make sure to taste a little food or drink in the morning, such as water, coffee, or tea, so that it will not be considered like one is fasting. The Peri Megadim writes this as well. This is the proper procedure for Rosh Hashanah and Simchat Torah as well if one knows that one will not have the opportunity to eat before midday. However, on Shabbat one must finish eating the Shabbat day meal early enough for one to be able to eat the third Shabbat meal as well.
At this time of year in Jerusalem, halachic midday is approximately 12:40 PM. In New York, it is at approximately 12:55 PM. One can find this time updated weekly or even daily in some of the more detailed Jewish calendars.