Artscroll’s calendars are excellent in that regard as far as most dates when not said. With that as a starting point, you then need to consult the Rov or Gabbai of the shul or minyan you daven with to ask about their own minhagos.
For example, in the main shul on Denver’s Westside, we stop saying Tachanun exactly 1 week before Rosh Chodesh Nissan, because during that week the Mishkan was being set up and taken down, with Moshe officiating as the Kohen. We don’t start again until 2 Iyar.