Beginning JavaScript®, Fourth Edition

Chapter 10. Date, Time, and Timers

Chapter 5 discussed that the concepts of date and time are embodied in JavaScript through the Date object. You looked at some of the properties and methods of the Date object, including the following:

• The methods getDate(), getDay(), getMonth(), and getFullYear() enable you to retrieve date values from inside a Date object.

• The setDate(), setMonth(), and setFullYear() methods enable you to set the date values of an existing Date object.

• The getHours(), getMinutes(), getSeconds(), and getMilliseconds() methods retrieve the time values in a Date object.

• The setHours(), setMinutes(), setSeconds(), and setMilliseconds() methods enable you to set the time values of an existing Date object.

One thing not covered in that chapter is the idea that the time depends on your location around the world. In this chapter you'll be correcting that omission by looking at date and time in relation to world time.

For example, imagine you have a chat room on your web site and want to organize a chat for a certain date and time. Simply stating 15:30 is not good enough if your web site attracts international visitors. The time 15:30 could be Eastern Standard Time, Pacific Standard Time, the time in the United Kingdom, or even the time in Kuala Lumpur. You could of course say 15:30 EST and let your visitors work out what that means, but even that isn't foolproof. There is an EST in Australia as well as in the United States. Wouldn't it be great if you could automatically ...