Yes, time is a construct. We parse up what is continuous into seconds, minutes, hours, days and years.
The fact that it is a social construct does not make it more “objective.” For example, we have a general understanding of “blue”, which helps us communicate. (Or, for that matter, those funny black marks have social meaning.”
I do think there is something objectively there beyond our social constructs; a flow of things. But because we need to make sense of it and function, so we give it names and units and metaphors.