Date and time in PHP

The date function

PHP has a very useful date function that can read in a Unix timestamp and output the date as a formatted string of your choice.

date(format [, optional Unix timestamp])

The timestamp is optional, if it is left out it will default to the current time.

Unix time stamps

An easy way to create Unix timestamps for use with the date function is to use mktime.

mktime([optional hour, minute, second, month, day, year])

All parameters in mktime are optional (from left to right i.e. if you want to specify a day then you have to specify a month), if they are left out they will default to the current date and time.

Date format string

Below are a list of common strings for the date function.

Format character	Description
a	am – pm
A	AM – PM
d	Day of the month – (01 – 31) – leading zeros
D	Day of the week – 3 letters e.g. Mon
F	Month of the year – full – e.g. January
g	12 hour format – (1 – 12 )
G	24 hour format – (0 – 23)
h	12 hour format – (01 – 12 ) – leading zeros
H	24 hour format – (00 – 23) – leading zeros
i	Minutes – (00 – 59) – leading zeros
j	Day of the month – (1 – 31) – no leading zeros
l	Day of the week – Full – e.g. Monday
L	Leap year – (1=leap year)
m	Month of the year – numerical – (01 – 12) – leading zeros
M	Month of the year – 3 letters – e.g. Jan
n	Month of the year – numerical – (1 – 12)
O	Difference to Greenwich mean time e.g. +0200
s	Seconds with leading zeros – (00-59)
S	Suffix of day of the month – e.g. st, nd, rd, th
t	Number of days in the month
T	Time zone
w	Numerical day of the week – (0 = Sunday, 1 = Monday)
W	Week of the year
Y	Year – full – 2005
y	Year – 2 numbers – 05
z	Day of year

For the full list see the PHP website.

Examples

Below are a list of example uses of the date function.

date('J MS Y');
//outputs the current date in the format: 1st Jan 2010

date('J MS Y', mktime(0, 0, 0, 1, 1, 2000));
//outputs 1st Jan 2000

PHP 5 DateTime object

As of PHP 5.2 you can create an object that represents the date and time.

$date = new DateTime('2011-01-31');
$datetime = new DateTime('2011-01-31 12:01:01');

Formatting the date

To format the date you use the same constants as before, but call the format method of the DateTime object.

$date = new DateTime('2011-01-31');
echo $date->format('j/n/Y');
//Outputs 31/1/2011