Javascript date parsing bug - fails for dates in June (??)

Question

I have some javascript which parses an ISO-8601 date. For some reason, it is failing for dates in June. But dates in July and May work fine, which doesn\'t make sense to m

Answer 1

The problem is that today is July 31.

When you set:

var date = new Date();

Then date.getUTCDate() is 31. When you set date.setUTCMonth(5) (for June), you are setting date to June 31. Because there is no June 31, the JavaScript Date object turns it into July 1. So immediately after setting calling date.setUTCMonth(5) if you alert(date.getUTCMonth()); it will be 6.

This isn't unique to June. Using your function on the 31st of any month for any other month that does not have 31 days will exhibit the same problem. Using your function on the 29th (non-leap years), 30th or 31st of any month for February would also return the wrong result.

Calling setUTC*() in such a way that any rollovers are overwritten by the correct value should fix this:

var date = new Date();
date.setUTCMilliseconds(0);
date.setUTCSeconds(parseInt(matches[6], 10));
date.setUTCMinutes(parseInt(matches[5], 10) - offset);
date.setUTCHours(parseInt(matches[4], 10));
date.setUTCDate(parseInt(matches[3], 10));
date.setUTCMonth(parseInt(matches[2], 10) - 1);
date.setUTCFullYear(parseInt(matches[1], 10));