Of course time exists. Just because its a human construction doesnt mean it doesnt exist, anymore than this PC doesnt exist for the house Im in doesnt exist.
Sure, we're all temporal constructs based upon the idea that we are born, we grow, we (at some point) die. This lends us to a teleological frame of reference, its the simplest way of looking at life. Though, you can modify this and say that time in a teleological way doesnt exist, maybe its cyclical or contingent but this doesnt mean that our artifically created reference point is any less valuable, than say a metre or a gram or an ounce.