When should the Zakat year be calculated for money that was in the possession of a speculator but was not invested, and is the owner of the money sinful for delaying Zakat for two years?

The shared land is either for the purpose of acquisition (qinyah) or for the purpose of trade.

First: If it is for the purpose of acquisition (use, not sale): You pay zakat on your share of its price (inheritance and partnership) when a hawl (full lunar year) passes after its sale, provided it reaches the nisab (minimum threshold). If you did not pay zakat on it previously without a valid excuse, then you are sinful and repentance is incumbent upon you. However, if you were ignorant of the ruling, an ignorance that is excusable, then there is no sin upon you.

Second: If it is for the purpose of trade: It is considered a trade commodity, and zakat is obligatory on it before its sale when a hawl passes on the original capital with which you purchased it, every year, if your share reaches the nisab. - Your share from the partnership: You pay zakat on it when the first hawl passes, before its sale. - Your share from the inheritance: You begin a new hawl for it from the day it is sold, and you pay zakat on it when its hawl is completed, even if it does not reach the nisab on its own, because it reaches the nisab when combined with your share from the partnership.