Generally, it is based on the timing of the distributions and where you lived at the time.
However, if you are part of a partnership and you have a business operating in the one state, you would be taxed by that state for the entire year.
For example, if you are part of an LLC that operates in CA and earns income in CA all year, you would need to file both a part year resident and a non resident return for CA and then a part year VT return.