Revivim:
Letting Purim joy last all year- and when to have a Friday seuda
If Purim falls on Friday, the custom is preferably to begin the meal before noon, but there are other possibities (see below). Purim joy was observed even when the Jewish people were in harsh exile It is an answer to suffering, since in Purim we learned that even evil will eventually turn to good, so it is the greatest joy of all
