From http://www.php.net/date :

a Lowercase Ante meridiem and Post meridiem am or pm

A Uppercase Ante meridiem and Post meridiem AM or PM

B Swatch Internet time 000 through 999

d Day of the month, 2 digits with leading zeros 01 to 31

D A textual representation of a day, three letters Mon through Sun

F A full textual representation of a month, such as January or March January through December

g 12-hour format of an hour without leading zeros 1 through 12

G 24-hour format of an hour without leading zeros 0 through 23

h 12-hour format of an hour with leading zeros 01 through 12

H 24-hour format of an hour with leading zeros 00 through 23

i Minutes with leading zeros 00 to 59

I (capital i) Whether or not the date is in daylights savings time 1 if Daylight Savings Time, 0 otherwise.

j Day of the month without leading zeros 1 to 31

l (lowercase 'L') A full textual representation of the day of the week Sunday through Saturday

L Whether it's a leap year 1 if it is a leap year, 0 otherwise.

m Numeric representation of a month, with leading zeros 01 through 12

M A short textual representation of a month, three letters Jan through Dec

n Numeric representation of a month, without leading zeros 1 through 12

O Difference to Greenwich time (GMT) in hours Example: +0200

r RFC 822 formatted date Example: Thu, 21 Dec 2000 16:01:07 +0200

s Seconds, with leading zeros 00 through 59

S English ordinal suffix for the day of the month, 2 characters st, nd, rd or th. Works well with j

t Number of days in the given month 28 through 31

T Timezone setting of this machine Examples: EST, MDT ...

U Seconds since the Unix Epoch (January 1 1970 00:00:00 GMT) See also time()

w Numeric representation of the day of the week 0 (for Sunday) through 6 (for Saturday)

W ISO-8601 week number of year, weeks starting on Monday (added in PHP 4.1.0) Example: 42 (the 42nd week in the year)

Y A full numeric representation of a year, 4 digits Examples: 1999 or 2003

y A two digit representation of a year Examples: 99 or 03

z The day of the year 0 through 366

Z Timezone offset in seconds. The offset for timezones west of UTC is always negative, and for those east of UTC is always positive. -43200 through 43200