You cease being a California resident on the day you leave the state for more than a temporary absence. I wouldn't matter that you still owned property there, that doesn't make you a resident.

Thank you.   We would not have moved if the house had not sold.   We left 2 days prior because we had the carpets cleaned.  If the house had fallen out of escrow,  we would have moved our stuff back in and stayed.   We went to our vacation home we own in Oregon and put our belongings in storage.  Once the house in California closed,  that is when it became more than a temporary absence.   Correct?

 The date you closed the sale of your CA house is a very reasonable choice as your first day of being a resident of OR.

You have some flexibility in choosing the date you ceased being a CA resident and began to be an OR resident.

The date you choose as the first day of residency in a new state (or country)  can also coincide with one of the following events: 

• You or your spouse arrived in the new state or country 
• Your belongings arrived 
• You or your spouse started work 
• You started renting your new place 
• You purchased your new home 
• You or a family member enrolled in school 
• You or your spouse registered to vote 
• You or your spouse applied for a state driver's license