The Indicators are based on atomic clocks and synchronised Along with the worldwide program of clocks that help Coordinated Common Time. India's time zone is based on the 82.5°E meridian, which passes via Mirzapur. The half-hour offset was chosen to help keep the time close to the signify solar time https://ist-world-clock43316.scrappingwiki.com/2467562/rumored_buzz_on_ist_to_gmt