A date is an object whose base is a number of milliseconds and that is displayed in a variety of formats by converting milliseconds in year, month, day ...
An object Date is created by a call to a constructor whose format is as follows:
new Date() new Date(millisecondes) new Date(year, month, day [, hour, minutes, seconds, milliseconds]) // arguments are integers new Date(text) // a string containing a date
If there is no argument, the default is the current day and time, when the constructor is called.
In case the argument is a date in the textual form, its format must be recognised
by the Date.parse method.
Apr 16, 2008
The parse method also recognizes the IETF format, as:
Mon, 16 Apr 2008 12:20:05 GMT
The number of milliseconds is since January 1, 1970. Milliseconds are useful for durations, otherwise using dates is preferable.
UTC and GMT formats are supported
GMT means Greenwich Mean Time. It's a solar time measured Observatory at Greenwich, England.
UTC means Coordinated Universal Time. Unit is an international standard which replaces GMT, which is based on atomic time rather than on the Earth's rotation. It is defined by ISO 8601.
Calculating the difference between two dates
The Date object supports arithmetic operations. In practice, we use mostly subtraction for the time elapsed between two dates.
var start = new Date(1000, 01, 01);
var finish = new Date(2011, 10, 15);
var diff = new Number((finish.getTime() - start.getTime()) / 31536000000).toFixed(0);
Simple way to know the date of the day
It is obtained by creating a Date object without argument. For instance with the following script:
And the day of the week
The day of the week is displayed with an array of names, and the getDay() method which returns the number starting from 1.