Navigator 2.0, Internet Explorer 3.0
date.getTimezoneOffset()
none
The difference, in minutes, between Greenwich Mean Time (GMT) and the local time.
getTimezoneOffset() returns the number of minutes difference between the GMT or UTC time zone and the local time zone. In effect, this function tells you what time zone the JavaScript code is running in. The return value is measured in minutes, rather than hours, because some countries have time zones that are not at even one-hour intervals.
getTimezoneOffset() is invoked through a Date object. Note, however, that it doesn't actually reference the Date object, and so it ought to be an independent function instead of a method.