Grenada uses the Atlantic Standard Time (AST). Grenada is four hours behind Greenwich Mean Time (GMT). Greenwich Mean Time is the clock time at the Royal Observatory in Greenwich, London. It is the reference point for every time in the world. In relation to Grenada, Grenada is four hours behind Greenwich Mean Time. For example, when the time in the UK is 4pm, it is only 12pm in Grenada.
Each time zone is based upon the degrees of latitude, and every 15 degree latitude starts a new time zone. In total, there are twenty-four (24) time zones in the world. Grenada has the same time zone as other Caribbean islands that are nearby - Saint Lucia, Guadeloupe, Trinidad and Tobago.
View here to convert time zones.
Credits: View here