Greenwich Mean Time can be converted to India Standard Time by moving ahead 5.5 hours. For example, at midnight GMT, the time is 5:30 a.m. IST. The conversion between GMT and IST may vary during daylight savings time depending on which cities adopt the time change.
GMT is used in the United Kingdom during the winter. GMT can also be referred to as Western European Time.
IST is used in India and Sri Lanka. It is one of the few time zones off by a half hour from GMT. IST was established by the Indian government in 1947, and it is based on 82.5 east degrees longitude.