The date function takes the format:
string date (string $format)
The $format string uses the following characters to represent different formatting options.
Day
d-Day of the month, 2 digits with leading zeros
D-A textual representation of a day, three letters
j-Day of the month without leading zeros 1 to 31
l-A full textual representation of the day of the week
N-ISO-8601 numeric representation of the day of the week (1 for Monday through 7 for Sunday)
S-English ordinal suffix for the day of the month
w-Numeric representation of the day of the week (0 for Sunday through 6 for Saturday)
z-The day of the year (starting from 0)
Week
W-ISO-8601 week number of year, weeks starting on Monday
Month
F-A full textual representation of a month, such as January or March
m-Numeric representation of a month, with leading zeros
M-A short textual representation of a month, three letters
n-Numeric representation of a month, without leading zeros
t-Number of days in the given month
Year
L-Whether it's a leap year
o-ISO-8601 year number.
Y-A full numeric representation of a year
y-A two digit representation of a year
Time
a-Lowercase Ante meridiem and Post meridiem (am or pm)
A-Uppercase Ante meridiem and Post meridiem (AM or PM)
B-Swatch Internet time
g-12-hour format of an hour without leading zeros
G-24-hour format of an hour without leading zeros
h-12-hour format of an hour with leading zeros
H-24-hour format of an hour with leading zeros
i-Minutes with leading zeros
s-Seconds with leading zeros
u-Microseconds
Timezone
e-Timezone identifier
I-Whether or not the date is in daylight saving time
O- Difference to Greenwich time (GMT) in hours
P-Difference to Greenwich time (GMT) with colon between hours and minutes
T-Timezone abbreviation
Z-Timezone offset in seconds. The offset for timezones west of UTC is always negative, and for those east of UTC is always positive.
Full Date/Time
c-ISO 8601 date
r-RFC 2822 formatted date
U-Seconds since the Unix Epoch (January 1 1970 00:00:00 GMT)