Tokyo is 7-8 hours ahead of Oslo. Oslo uses Central European Time (CET/CEST, UTC+1/+2) while Tokyo uses Japan Standard Time (JST, UTC+9). During standard time, Tokyo is 8 hours ahead; during daylight saving time, Tokyo is 7 hours ahead.
Japan does not observe daylight saving time, while Norway does, so the difference varies seasonally.
Best calling time: 1:00 AM - 10:00 AM Oslo time. This corresponds to 9:00 AM - 6:00 PM in Tokyo during daylight saving time. Early morning calls from Oslo work best.
Oslo and Tokyo represent two very different but highly developed societies. Both are known for high quality of life and innovation. Direct flights via connections take about 12-14 hours.