Change of Use on a primary residence.

We live in a our primary residence home, then we end up purchasing a secondary home which we plan on moving into to once renovations are complete. We took possession of the secondary home end of October 2023. Since renovations needed to occur for this new property, we continued to live in the first home up until the end of the year of Dec 31, 2023. We had an opportunity to rent out the first property, so we did so for January 1 2024 and moved into my in-laws until and will stay here until the renovations are complete for the secondary property,. This secondary porperty will become our family home. My questions are, when do you realize a Change of Use on a property, is it the year that the change of use occurs or is it the time that we took possession of the secondary home? We need to make an election on a primary residence address as well, because we technically owned two properties before the end of the tax year, do we need to claim the new property as our primary residence even though we have not moved into the property due to renovations?