UTC is the universal standard time coordinated through international agreement. It is used as the official
time around the world. UTC is determined by adding a leap second to GMT (Greenwich Mean Time),
which is determined through astronomical measurement, in order to keep the precise time.
Japan Standard Time (JST) is 9 hours ahead of UTC (+ 9 hours).
Summer time is daylight saving time. Advancing the watch one hour to prolong daytime during longer
daylight hours in summer. Daylight saving time has been adopted in about 80 countries, mainly in Europe
and North America. The adoption and duration of daylight saving time vary depending on the country.
Germany
Japan
U.S.A.
The equator
Date line