One may not perform work on Erev Pesach past Halachic midday. Halachic midday is at approximately 1:00 pm in New York City. In Jerusalem, halachic midday is at approximately 12:45 pm.
There are two reasons for the prohibition of performing work on Erev Pesach. The first is so that one does not become overly involved in his work and slack off in his preparations for the Seder night. This is the opinion of Rashi and the Meiri (Pesachim 50a).
Others explain that the reason for prohibiting work is because when the Bet Hamikdash stood, it was prohibited for any Jew to perform work after Halachic midday for this was the time for the sacrificing of the Korban Pesach (Pesach offering). Even regarding the rest of the year, when one brought an offering to the Bet Hamikdash, that day is the owner’s private holiday and he is forbidden to perform any work, however, regarding the Korban Pesach, since it can only be brought from Halachic midday and on, only then is it considered a holiday. Even after the Bet Hamikdash was destroyed and the Korban Pesach was nullified because of our sins, the decree banning performance of work was not nullified since this was prohibited by the decree of our Sages on the entire Jewish nation, it remains forbidden forever; this is the case for all decrees made by our Sages through a Bet Din (rabbinical court), that although the reason for the enactment no longer exists, the enactment itself is still not nullified. This reason is the main one, halachically speaking.
There are places that customarily do not perform work on Erev Pesach even before halachic midday. Indeed, this is the custom of the holy city of Jerusalem, that work is not performed the entire day.
The only kind of work that is prohibited on Erev Pesach is full-fledged work, such as producing new vessels or sewing new clothes. However, one may fix vessels, for instance mending torn clothes. Similarly, one may deal with merchandise and make business deals as well as write and polish one’s shoes. Also, one may cut his nails, however, shaving and taking a haircut is prohibited unless one is doing so through a non-Jewish barber, in which case one may be lenient. It is most preferable though to take a haircut and shave before halachic midday. In a place where it is customary not to perform work on Erev Pesach even before halachic midday, one should take care to take a haircut and shave on the Thirteenth of Nissan (or on the night of the Fourteenth).
