Technically the new pass starts after the expiration of the old one. Example: My SoCal pass exired 4/28. On 4/6, I renewed for next year and upgraded to Premium. They took my SoCal pass and gave me a Premium. The Premium pass didnt technically start until 4/29, but they said I would have access to all of the higher merchandise and food options. Parking and not having blackout days would not be available until 4/29. That being said, I went to the park intending to buy a blackout ticket for 4/27 and they just overrode the blackout for me and let me in without paying for the blackout ticket. I didnt even ask, they just told me not to worry about it when I went to buy the ticket and gave me something to show the people at the gate.