Most Jews begin the Purim meal in the afternoon, after praying Minĥa. During the morning hours, they are busy sending mishlo’aĥ manot to one another and giving matanot la-evyonim, going out of their way to express love and friendship toward family and friends. When afternoon arrives, it is proper to pray Minĥa before starting the meal; otherwise there is reason to be concerned that people will not be able to pray Minĥa due to drunkenness.
Some people start the meal very late, just before shki’a, eating most of the meal after dark. Many authorities question this practice, as the mitzva is to eat the meal on Purim, and at tzeit ha-kokhavim the next day already begins. Some answer this objection by pointing out that everything follows the beginning, and since these people start the meal on Purim, its continuation at night is still considered part of the Purim meal. The same rule applies to Birkat Ha-mazon. If one starts the meal during the day and finishes it late at night, he nonetheless recites Al Ha-nisim in Birkat Ha-mazon. Furthermore, it is appropriate to rejoice on the night immediately following the fourteenth of Adar as well, because that is when Purim begins in walled cities. Le-khatĥila, however, it is proper to start the meal when there is plenty of time left in the day. Then, if the meal carries over into the night, no harm is done, because the main part of the meal was eaten during the day.
Some say that it is preferable to perform the mitzva as early as possible and eat the meal in the morning. This way, whoever gets drunk can become sober by Minĥa time. The prevalent custom, however, is to conduct the meal in the afternoon.
It is praiseworthy to study some Torah before beginning the se’uda, as it is written, “The Jews enjoyed light and gladness, joy and honor” (Esther 8:16); the Sages expound, “‘Light’ refers to Torah.” Through Torah study, one can attain consummate joy (Rema 695:2).
According to many authorities, one who knows that he may not be able to pray Minĥa or Ma’ariv if he gets drunk should not get drunk (Ĥayei Adam, bhl). However, R. Avraham Yitzĥak Kook writes that one who drinks on Purim is engaged in performing a mitzva, and the rule is that one who is engaged in performing a mitzva is exempt from performing another mitzva (Oraĥ Mishpat, omissions §7).