IST: IST is the Indian Standard Time and is the time zone used in India which is 5 hours and 30 minutes ahead of Greenwich Mean Time (GMT). This time zone is followed across the entire country of India. The longitudinal difference between India's easternmost and westernmost points is approximately 30 degrees, that is 68 ° 7 ' E to 97 ° 25 ' E. The time difference is almost two hours may cause many anomalies and to overcome these difficulties, the local time of a line of longitude passing mid-the way through the country is taken as the Standard Meridian and has been accepted for the calculation of the time of the entire country. The local time of 82 ° 30 ' East of longitude which passes through India is known as the Indian Standard Time (IST)