Returns a date converted to a string using Greenwich Mean Time(GMT).
The required dateObj reference is any Date object.
The toGMTString method is obsolete, and is provided for backwards compatibility only. It is recommended that you use the toUTCString method instead.
The toGMTString method returns a String object that contains the date formatted using GMT convention. The format of the return value is as follows: "05 Jan 1996 00:00:00 GMT."