You usually can’t spectate a clan war until the war ends if you joined the clan after that war started, or if you weren’t selected for the war roster. Clash of Clans also marks you as ineligible for war until the previous war is over, so the restriction is tied to the ongoing war rather than a fixed number of days.

What this means

  • If you join during an active war , you can only spectate that war.
  • If you were already in the clan but not picked for that war, you also can’t participate, only spectate.
  • Once the war finishes, the restriction ends.

Simple example

If you join a clan on Tuesday and the clan’s war is already running, you’ll usually have to wait until that war completes before normal war participation is available again.

Bottom line

There is no standard “X days” spectate ban for this in the war system. The wait is generally until the current war ends.

TL;DR: after joining a new clan, you can’t spectate/participate in that clan war properly until the ongoing war is finished.