The half-year (or 183 days) business you sometimes see, refers to someone who moves in, and then moves out....but you've remained in CO, so you are over the half year already...and probably intend to remain....at least for awhile yet.
Even people who move into CO in December can be considered to be part year residents for that year, if they've moved their self, household goods, etc into CO and intend to remain for at least half a year.
Exceptions...College students with parents in another state who claim them as a dependent....they can be there 9 mos, or even all year, and they are still considered nonresidents, and do not file in CO unless they actually work a job in CO during the year.
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
