I will resolve based on the (de facto) end date on this Wikipedia page:

https://en.m.wikipedia.org/wiki/Russian_invasion_of_Ukraine

I will wait until the end date has been the same for a full 7 day period.

If the article is renamed, split or merged I will update the link above to the closest equivalent article.

I will resolve in line with the Wikipedia editors unless it's clear that this is not in line with the "spirit" of the question.

The spirit of the question is about when the armed conflict substantially stops regardless of who controls what territory. A temporary ceasefire does not count.

I may change the criteria to clarify questions or fix flaws.

I will not bet in this market.