How to Create a True Copy of a Date Object in JavaScript?

Avoiding Date Object Mutability: Cloning Date Instances

When assigning a Date variable to another, the reference to the same instance is copied. Altering one instance affects the other. To create a true copy or clone of a Date instance, circumvent this behavior.

Solution:

Utilize the Date object's getTime() method, which retrieves the number of milliseconds elapsed since the epoch time (1 January 1970 00:00:00 UTC):

var date = new Date();  // Create the original Date object
var copiedDate = new Date(date.getTime());  // Clone the Date object

In Safari 4, an alternative approach is possible:

var date = new Date();  // Create the original Date object
var copiedDate = new Date(date);  // Clone the Date object

However, the compatibility of the latter approach across browsers is uncertain. It appears functional in IE8.

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