hershi:- Litvaks skip Tachnun, all of Nisson; Yom ha’Atzma’ut; Mincho of Pesach Sheni; Lag b’Omer; Yom Yerusholayim; Rosh Chodesh Sivan thru Isru Shovu’os; Tisho b’Ov {this year Assoro b’Ov for 1st time in 14 years}; Chag haMecholos [A.K.A. Chamisho Ossor b’Ov}; Erev R’H & R’H; Erev Y’K thru Isru Simchas Toroh; Chanukah; Chamisho Ossor b’Ov; Purim & Shushan Purim [including Koton thereof]; Friday afternoons & Rosh Chodesh.
However Litvaks do recite Tachnun from 2 days after Shovu’os, and from 2 days after Simchas Toroh thru Rosh Chodesh marCheshvon.