I agree as well. We have had many issues with timelines being unrealistic becasue they are set from above instead of by the people actually doing the work. In addition we miss holidays, forget to consider production (we are a 24/7 facility with little room for shifting), and one big one is forgetting to account for other countries holidays/ schedules. For example, we work a lot with Germany and their sense of urgency on projects is often very different than ours. They also seem to take much more vacation than we do especially in December which can really hurt a project.

One suggestion I have is to discuss the timeline with all parties before deciding on it- though unexpected things crop up, it is better to have all parties on board at the start.