Determine the difference in minutes between the time on the host computer and Greenwich Mean Time (GMT).
The getTimezoneOffset method returns an integer value representing the number of minutes between the current machine and GMT. These values are appropriate to the computer the script is executed on. If it is called from a server script, it returns values appropriate to the server. It is called from a client script, the return value appropriate to the client.
For example, a server in New York City is contacted by a client in Los Angeles on December 1. getTimezoneOffset returns -480 if executed on the client, or -300 if executed on the server.