Timer in workflow based on variable/date does not work.

I added a timer to my workflow to wait until a certain date/hour(variable date called end_of_change in my form) to create the second task. However, once I closed the first task it creates the second one. I want my workflow to wait a determine hour to create the task. I don't see what I am doing wrong.

Script:

answer = gs.dateDiff(gs.nowDateTime(), current.variables.end_date_change1.getDisplayValue(), true);