There is a tax concept called domicile. Your domicile is more than just your current living address. It is where you maintain a significant social, legal, and family ties. It is your true home in the sense of “your home is where your heart is.“ You can only have one domicile at a time, even though you may have many places to live.
California seems to follow this principle, based on a quick review of their rules for determining residency. (I did not see a strict number of day limit, such as New York State has.) If your domicile is overseas and you are only in California for a quick or transitory purpose, then you are a non-resident. But you would still be required to report and pay California state income tax on California source income earned while in California. If your visit was not temporary or transitory(such as the 6+ months were consecutive), you would probably be considered a part year California resident, and as a California resident you will be required to report and pay tax on your worldwide income earned while in California.
Or, you might be domiciled in California and considered to be “temporarily” out of the country when you are, in which case you are fully a California resident.
Although California does not seem to have a strict limit on the number of days, California is known to be very aggressive in enforcing their residency rules and determining that people are residents in order to have them pay more taxes.
Review the rules and instructions at this link.
https://www.ftb.ca.gov/file/personal/residency-status/part-year-and-nonresident.html
