Soft Fixed time mass edit

Hi there. I have a question regarding soft fixed timing in playlist. Im currently importing my playlists (from another scheduling soft as m3u) into DB with first DUMMY element.

Is it possible to mass edit first element in hour (that dummy) as soft fixed time (so that playlist starts at the top of the hour (after the element from previous hour finishes). I dont want to do it manually for every hour of weekly playlist.