"You have time."
"var" is used to describe the existence of something. Turkish doesn't have a specific word for "to have."
If you are talking about a having a general direct object, you normally use "var." If you are talking about a specific direct object, you normally use a structure with the locative :)
So this doesn't really work for two reasons.
1) The possessive structure with the locative case (like what you wrote) is used to denote specific objects in sentences showing possession. The above sentence is not specific.
2) This structure is also mostly (but not exclusively) used for physical items and not really with concepts. The Turkish sentence is literally describe the location of the object, and an abstract concept like "time" can't really have a location :)