Megillah 1:1-2

Megillah 1:1

The Megillah is potentially read on 11, 12, 13, 14 and 15 Adar, no earlier and no later. Cities surrounded by walls from the time of Joshua read on 15 Adar (Shushan Purim); villages and big cities read it on 14 Adar (Purim) but villages can push the reading up to the market days.

Megillah 1:2

If 14 Adar fell on a Monday, villages and big cities would read on that day and walled cities would read on the next day. If it fell on a Tuesday or a Wednesday, villages would read earlier on the market day (i.e., Monday), big cities would read on that day, and walled cities would read on the next day. If it fell on a Thursday, villages and big cities would read on that day and walled cities on the next day. If it fell on Friday, villages would read earlier on the market day (i.e., Thursday), and big cities and walled cities would read on that day. If it fell on Shabbos, villages and big cities read earlier on the market day (Thursday) and walled cities would read on the day after. If it fell on Sunday, villages read earlier on the market day (Thursday), big cities read on that day, and walled cities read on the next day.