PHP mktime sometimes returning wrong day

Question

I'm having a simple problem with mktime. I'm finding the following code:

echo date("Y-M-d", mktime(11, 45, 0, 01, 05, 2014)); echo ", ";
echo date("Y-M-d", mktime(11, 45, 0, 01, 06, 2014)); echo ", ";
echo date("Y-M-d", mktime(11, 45, 0, 01, 07, 2014)); echo ", ";
echo date("Y-M-d", mktime(11, 45, 0, 01, 08, 2014)); echo ", ";
echo date("Y-M-d", mktime(11, 45, 0, 01, 09, 2014)); echo ", ";

is producing the following output:

2014-Jan-05, 2014-Jan-06, 2014-Jan-07, 2013-Dec-31, 2013-Dec-31

The date function is just there to make it more readable; the timestamps returned by mktime themselves are wrong. The only thing changing is the day of the month, so I don't know why there would be a discontinuity between the day being 7 and 8, or why both the 8 and the 9 return the same day.

I've checked that the hour, minute, and second don't change the result of having the wrong day, though they do change the exact timestamp. That is, the last two lines above return the exact same timestamp (1388508300) but if I change the hour, the relative change in the timestamp is as expected.

In case context matters, this is being run in PHP 5.3 within a WordPress installation.

Answer 1

Integer literals starting with 0.. are in octal notation. 08 in octal or above does not exist, you're getting entirely wrong values. The value for the fifth day is 5, not 05 and so on.

Answer 2

Get rid of the leading zeros before your days (and months)

echo date("Y-M-d", mktime(11, 45, 0, 1, 5, 2014)); echo ", ";
echo date("Y-M-d", mktime(11, 45, 0, 1, 6, 2014)); echo ", ";
echo date("Y-M-d", mktime(11, 45, 0, 1, 7, 2014)); echo ", ";
echo date("Y-M-d", mktime(11, 45, 0, 1, 8, 2014)); echo ", ";
echo date("Y-M-d", mktime(11, 45, 0, 1, 9, 2014)); echo ", ";

See it in action