Sri Lanka Standard Time (SLST) is the time zone for Sri Lanka. It is 5 hours and 30 minutes ahead of GMT/UTC (UTC+05:30).The Sri Lanka Time reverted on 15 April 2006 to match Indian Standard Time calculated from the Allahabad Observatory in India 82.5 ° longitude East of Greenwich, the reference point for GMT.The entire country shares the same time. Since 1880, Ceylon or Sri Lanka Time has varied between UTC+05:30 to UTC+06:30.In 1880, it was UTC+05:30.