The time difference between California and Hawaii is two hours. California is in the Pacific Time Zone, which is two hours behind the Hawaiian Standard Time Zone. This means that when it is 10:00am in California, it is 12:00pm in Hawaii. The difference is due to the fact that Hawaii does not observe Daylight Saving Time. California does, which is why the difference is two hours most of the year. During Daylight Saving Time, the difference between the two time zones increases to three hours.
The two time zones are offset from each other because Hawaii is located in the middle of the Pacific Ocean, near the International Date Line. As a result, Hawaii is the last state in the United States to observe the start and end of each day. This is why the time difference between California and Hawaii is two hours most of the year.