JavaScript: The Definitive Guide

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Variables and Data Types

3.10 The Date Object

The sections above have described all of the fundamental data types supported by JavaScript. Dates and times are not one of these fundamental types. But JavaScript does provide a type (or class) of object that represents dates and times, and can be used to manipulate this type of data. A Date object in JavaScript is created with the new operator and the Date() constructor:

now = new Date();   // create an object representing the current date and time
xmas = new Date(96, 11, 25);  // Create a Date object representing Christmas

Methods of the Date object allow you to get and set the various date and time values, and to convert the Date to a string, using either local time or GMT time. For example:

xmas.setYear(xmas.getYear() + 1);    // Change the date to next Christmas
document.write("Today is: " + now.toLocaleString());
In addition, the Date object also defines functions (not methods; they are not invoked through a Date object) to convert a date specified in string or numeric form to an internal millisecond representation that is useful for some kinds of date arithmetic.

You can find full documentation on the Date object and its methods in the reference section of this book. Unfortunately, the Date object is plagued with various bugs in Navigator 2.0. Appendix B, Known Bugs, contains details.

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