new
Date
(
2015
,
0
);
// 12:00 A.M., Jan 1, 2015
new
Date
(
2015
,
1
);
// 12:00 A.M., Feb 1, 2015
new
Date
(
2015
,
1
,
14
);
// 12:00 A.M., Feb 14, 2015
new
Date
(
2015
,
1
,
14
,
13
);
// 3:00 P.M., Feb 14, 2015
new
Date
(
2015
,
1
,
14
,
13
,
30
);
// 3:30 P.M., Feb 14, 2015
new
Date
(
2015
,
1
,
14
,
13
,
30
,
5
);
// 3:30:05 P.M., Feb 14, 2015
new
Date
(
2015
,
1
,
14
,
13
,
30
,
5
,
500
);
// 3:30:05.5 P.M., Feb 14, 2015
// creates dates from Unix Epoch timestamps
new
Date
(
0
);
// 12:00 A.M., Jan 1, 1970 UTC
new
Date
(
1000
);
// 12:00:01 A.M., Jan 1, 1970 UTC
new
Date
(
1463443200000
);
// 5:00 P.M., May 16, 2016 UTC
// use negative dates to get dates prior to the Unix Epoch
new
Date
(
-
365
*
24
*
60
*
60
*
1000
);
// 12:00 A.M., Jan 1, 1969 UTC
// parsing date strings (defaults to local time)
new
Date
(
'June 14, 1903'
);
// 12:00 A.M., Jun 14, 1903 local time
new
Date
(
'June 14, 1903 GMT-0000'
);
// 12:00 A.M., Jun 14, 1903 UTC
If you’re trying these examples out, one thing you’ll notice is that the results you get
are always in local time. Unless you are on UTC (hello, Timbuktu, Madrid, and
Greenwich!), the results listed in UTC will be different than shown in this example.
This brings us to one of the main frustrations of the JavaScript
Date
object: there’s no
way to specify what time zone it should be in. It will always store objects internally as
UTC, and format them according to local time (which is defined by your operating
system). Given JavaScript’s origin as a browser-based scripting language, this has tra‐
ditionally been the “right thing to do.” If you’re working with dates, you probably
want to display dates in the user’s time zone. However, with the global nature of the
Internet—and with Node bringing JavaScript to the server—more robust handling of
time zones would be useful.
Moment.js
While this book is about the JavaScript language itself—not libraries—date manipula‐
tion is such an important and common problem that I have decided to introduce a
prominent and robust date library, Moment.js.
Moment.js comes in two flavors: with or without time zone support. Because the time
zone version is significantly larger (it has information about all the world’s time
zones), you have the option of using Moment.js without time zone support. For sim‐
plicity, the following instructions all reference the time zone–enabled version. If you
want to use the smaller version, visit
for information about your
options.
If you’re doing a web-based project, you can reference Moment.js from a CDN, such
as cdnjs:
Moment.js | 221
