What would cause your manager to make you come in at an earlier time than usual?

I tell them the schedule i want and they wont change it. Im only available from this time to this time on these certain days. I asked for 2/3pm til close Thursday thru sunday. And have 3 days off in a row. I asked for it that way and thats how i prefer it. As people you need to do whats right for you. Dont let them do it for you. And they legally cant do anything about it. That way I have more time to myself. Sleep 7/9 hours. 7 hours of work. And 7 hours to myself.