The following characters are recognized PHP date formats:

a	"am" or "pm"
A	"AM" or "PM"
B	Swatch Internet time
d	day of the month, 2 digits with leading zeros; i.e. "01" to "31"
D	day of the week, textual, 3 letters; e.g. "Fri"
F	month, textual, long; e.g. "January"
g	hour, 12-hour format without leading zeros; i.e. "1" to "12"
G	hour, 24-hour format without leading zeros; i.e. "0" to "23"
h	hour, 12-hour format; i.e. "01" to "12"
H	hour, 24-hour format; i.e. "00" to "23"
i	minutes; i.e. "00" to "59"
I	"1" if Daylight Savings Time, "0" otherwise.
j	day of the month without leading zeros; i.e. "1" to "31"
l	day of the week, textual, long; e.g. "Friday"
L	boolean for whether it is a leap year; i.e. "0" or "1"
m	month; i.e. "01" to "12"
M	month, textual, 3 letters; e.g. "Jan"
n	month without leading zeros; i.e. "1" to "12"
O	Difference to Greenwich time in hours; e.g. "+0200"
r	RFC 822 formatted date; e.g. "Thu, 21 Dec 2000 16:01:07 +0200" (added in PHP 4.0.4)
s	seconds; i.e. "00" to "59"
S	English ordinal suffix for the day of the month, 2 characters; i.e. "st", "nd", "rd" or "th"
t	number of days in the given month; i.e. "28" to "31"
T	Timezone setting of this machine; e.g. "EST" or "MDT"
U	seconds since the Unix Epoch (January 1 1970 00:00:00 GMT)
w	day of the week, numeric, i.e. "0" (Sunday) to "6" (Saturday)
W	ISO-8601 week number of year, weeks starting on Monday (added in PHP 4.1.0)
Y	year, 4 digits; e.g. "1999"
y	year, 2 digits; e.g. "99"
z	day of the year; i.e. "0" to "365"
Z	timezone offset in seconds (i.e. "-43200" to "43200"). The offset for timezones west of UTC is always negative, and for those east of UTC is always positive.