Japan's standard time zone is UTC/GMT +9 hours during winter, and UTC/GMT +8 hours during summer. As a matter of fact, Japan doesn't switch to daylight saving time twice a year.
Japan only has one timezone : it's the same in Tokyo, Hokkaido, Kyoto or Okinawa. This timezone is officially called 日本標準時 Nihon Hyōjunji / 中央標準時 Chūō Hyōjunji / Japan Standard Time (JST).
- When it's noon in London GMT, it's 9PM in Tokyo during winter, or 8PM during summer
- When it's 5PM in New York, it's 7AM the next day in Tokyo during winter, or 6AM during summer
To ask "what time is it ?" in Japan, you have to say "Ima nan ji desu ka" 今何時ですか。