The millisecond representation of the specified Date object date; that is, the number of milliseconds between midnight (GMT) on 1/1/1970 and the date and time specified by date.
getTime( ) converts a date and time to a single integer. This is useful when you want to compare two Date objects or to determine the time elapsed between two dates. Note that the millisecond representation of a date is independent of the time zone, so there is no getUTCTime( ) method in addition to this one. Don't confuse this getTime( ) method with the getDay( ) and getDate( ) methods, which return the day of the week and the day of the month, respectively.
Date.parse( ) and Date.UTC( ) allow you to convert a date and time specification to millisecond representation without going through the overhead of first creating a Date object.