CODEWITHSUNDEEP
javascriptdate
EcoChan
EcoChan

Reputation: 83

Why 12.31.2013 last month is 12.01.2013?

Set the date:

var a = new Date('2013.12.31');

Output:

Tue Dec 31 2013 00:00:00 GMT+0800 (China Standard Time)

Modify date:

a.setMonth(a.getMonth()-1);

Modified output:

Sun Dec 01 2013 00:00:00 GMT+0800 (China Standard Time)

Upvotes: 2

Views: 60

Answers (1)

John Koerner
John Koerner

Reputation: 38079

30 days has September, April, June, and November. Subtracting 1 from the month portion of Dec 31 gives you Nov 31. Since Nov only has 30 days, the extra day puts it into December.

Upvotes: 7

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