 Tachanun is omitted from the prayers on Shabbat, all the major holidays and festivals (including "Chol HaMoed", the intermediate days of Pesach and Sukkot), "Rosh Chodesh" (new moon), Hanukkah and Purim, as these days are of a festive nature and reciting Tachanun, which is mildly mournful, would not be appropriate.The following is a list of all the other days, "minor holidays", when tachanun is excluded from the prayers, and Psalm 126 is recited during Birkat HaMazon.It is typically also omitted from the Mincha prayers the preceding afternoon, unless otherwise noted