Japan is 16 hours ahead of California during California's daylight saving time period (PDT). When California is on standard time (PST), Japan is 17 hours ahead. Japan does not observe daylight saving time. So, the time difference between Japan and California is:
- 16 hours ahead when California is observing daylight saving time (spring to fall)
- 17 hours ahead when California is on standard time (fall to spring).
