I don't think there was an official time. You'd likely have to go back and look at the quests and their respective items to fully gauge the time gap. For instance, one of the quest items in Heavensward, when examined, clearly states that at least a fortnight passed between you being told that the item was going to be made and then you receiving it. I plan on replaying myself here soon, so if I do see how much time has passed, I'll be sure to post here again!