I work for a smaller business (50 employees) and am the only one handling a fairly large project for a client. This project involves upgrading software on their server.
They are consistently pressuring me for an "upgrade date", but I can't give it to them. There is a lot of prep work that needs completed by myself and other people at their company. If I set a date and the prep work isn't done, the upgrade can't happen. It's also hard to estimate when the prep work will be done because we keep running into issues.
Neither myself or the other people at the clients company were around when the last upgrade took place. A lot of it is trial and error. So far I have just been trying to explain the situation and why a firm date can't be set. Their response is just that the "old server is being discontinued (by their company) so it needs upgraded immediately".