How to build recommendation system that also takes time as a feature Let's say a User was Interested in football, so we were recommending him posts about football after few days or weeks he starts watching Baseball.

How'd we go about building a recommender system that also takes recency into consideration
Or
Let's say that it knows when a user was interested in what
Use a diminishing sample weight where the newest sample = 1 and older samples get lower weights. This way if a user changes his interests over time, your recommendations will change accordingly.