5.1.1 JS Date Formats

JavaScript ISO Dates

• ISO 8601 is the international standard for the representation of dates and times.
• The ISO 8601 syntax (YYYY-MM-DD) is also the preferred JavaScript date format:

Example 1: JS Dates ISO Dates part 1

var d = new Date("2015-03-25");

• The computed date will be relative to your time zone.
• Depending on your time zone, the result above will vary between March 24 and March 25.

ISO Dates (Year and Month)

ISO dates can be written without specifying the day (YYYY-MM):

Example 2: JS Dates ISO Dates part 2

var d = new Date("2015-03");

Time zones will vary the result above between February 28 and March 01.

ISO Dates (Only Year)

ISO dates can be written without month and day (YYYY):

Example 3: JS Dates ISO Dates part 3

var d = new Date("2015");

Time zones will vary the result above between December 31 2014 and January 01 2015.

ISO Dates (Date-Time)

ISO dates can be written with added hours, minutes, and seconds (YYYY-MM-DDTHH:MM:SSZ):

Example 4: JS Dates ISO Dates part 4

var d = new Date("2015-03-25T12:00:00Z");

• Date and time is separated with a capital T.
• UTC time is defined with a capital letter Z.
• If you want to modify the time relative to UTC, remove the Z and add +HH:MM or -HH:MM instead:

Example 5: JS Dates ISO Dates part 5

var d = new Date("2015-03-25T12:00:00-06:30");

UTC (Universal Time Coordinated) is the same as GMT (Greenwich Mean Time).

Omitting T or Z in a date-time string can give different results in different browsers.

JavaScript Short Dates

Short dates are written with an "MM/DD/YYYY" syntax like this:

Example 6: JS new Date()

var d = new Date("03/25/2015");

JavaScript Long Dates

Long dates are most often written with a "MMM DD YYYY" syntax like this:

Example 7: JS new Date() part 2

var d = new Date("Mar 25 2015");

Month and day can be in any order:

Example 8: JS new Date() part 3

var d = new Date("25 Mar 2015");

And, month can be written in full (January), or abbreviated (Jan):

Example 9: JS new Date() part 4

var d = new Date("January 25 2015");

Example 10: JS new Date() part 5

var d = new Date("Jan 25 2015");

Commas are ignored. Names are case insensitive:

Example 11: JS new Date() part 6

var d = new Date("JANUARY, 25, 2015");

Date Input - Parsing Dates

• If you have a valid date string, you can use the Date.parse() method to convert it to milliseconds.
• Date.parse() returns the number of milliseconds between the date and January 1, 1970:

Example 12: JS Date.parse() part 1

var msec = Date.parse("March 21, 2012");
document.getElementById("demo").innerHTML = msec;

You can then use the number of milliseconds to convert it to a date object:

Example 13: JS Date.parse() part 2

var msec = Date.parse("March 21, 2012");
var d = new Date(msec);
document.getElementById("demo").innerHTML = d;