About Date & Time formats:

You can format the date & time in many ways, using the PHP syntax.
As quoted from the PHP manual, here are the letters you can use:

The following characters are recognized in the format string:
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; i.e. "Fri"
F - month, textual, long; i.e. "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 (capital i) - "1" if Daylight Savings Time, "0" otherwise.
j - day of the month without leading zeros; i.e. "1" to "31"
l (lowercase 'L') - day of the week, textual, long; i.e. "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; i.e. "Jan"
n - month without leading zeros; i.e. "1" to "12"
r - RFC 822 formatted date; i.e. "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, textual, 2 characters; i.e. "th", "nd"
t - number of days in the given month; i.e. "28" to "31"
T - Timezone setting of this machine; i.e. "MDT"
U - seconds since the epoch
w - day of the week, numeric, i.e. "0" (Sunday) to "6" (Saturday)
Y - year, 4 digits; i.e. "1999"
y - year, 2 digits; i.e. "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.

Unrecognized characters in the format string will be printed as-is.

For more information and examples, check the PHP manual on this page.