1,389. Taanis Esther; When Av Enters

Hilchos Taaniyos 5:5

The universal practice of Jewry is to fast on the aforementioned days and also on 13 Adar, in commemoration of the fasts that the Jews undertook in the time of Haman, as per Esther 9:31, “…the fasts and the outcries.” If 13 Adar falls on Shabbos, the fast is moved up to Thursday, 11 Adar. If any other fast falls on Shabbos, it is postponed until Sunday; if a fast falls on Friday, we fast on Friday. On these fasts, trumpets are not blown and Neilah is not recited. The Torah section “Vay’chal” is read at both shacharis and mincha. On all these fasts, we may eat and drink on the preceding night, with the exception of Tisha b’Av.

Hilchos Taaniyos 5:6

When the month of Av enters, we reduce forms of joy. During the week in which Tisha b’Av falls, we are not permitted to cut our hair, to do laundry, or to wear fresh clothes – not even of linen – until after Tisha b’Av. The longstanding universal practice is not to eat meat or to enter a bathhouse during this week until after Tisha b’Av. Some places also refrain from slaughtering animals for meat from Rosh Chodesh Av until after Tisha b’Av.

Please note that the practices described by the Rambam may not reflect our current observances.