PHP Date and Time Functions

The date Function

The date function outputs the current date and time in a specified format. The format is defined by control commands (English letters), and any separators can be inserted between them (hyphens, colons, etc.).

Here are these commands:

U – number of seconds since 1 January 1970 (i.e., timestamp).
z – day of the year.
Y – year, 4 digits.
y - year, two digits.
m – month number (with leading zero).
n – month number without leading zero.
d – day of the month, always two digits (the first can be zero).
j – day of the month without leading zero.
w – day of the week (0 - Sunday, 1 - Monday, etc.).
h – hours in 12- hour format.
H – hours in 24- hour format.
i – minutes.
s – seconds.
L – 1 if leap year, 0 if not leap year.
W – week number of the year.
t – number of days in the specified month.

Examples of Using date

<?php
	// All examples are shown for the date 01.06.2013 at 12.23.59, Monday
	
	echo date('Y'); // returns '2013'
	
	echo date('y'); // returns '13'
	
	echo date('m'); // returns '06' - month number
	
	echo date('d'); // returns '01' - day of the month
	
	echo date('j'); // returns '1' - day of the month (without leading zero)
	
	echo date('w'); // returns '1' - Monday
	
	echo date('H'); // returns '12' - hours
	
	echo date('i'); // returns '23' - minutes
	
	echo date('s'); // returns '59' - seconds
	
	echo date('d-m-Y'); // returns '01-06-2013'
	
	echo date('d.m.Y'); // returns '01.06.2013'
	
	echo date('H:i:s d.m.Y'); // returns '12:23:59 01.06.2013'
?>

The time Function

The time function returns the difference in seconds between 1 January 1970 and the current moment in time. This representation of a date is called the timestamp format. Using the time function we can only get the current moment in time. To get a timestamp for any date, use the mktime function. See the example:

<?php
	echo mktime(12, 43, 59, 1, 31, 2017);
?>

The mktime Function

The mktime function returns a timestamp for a specified moment in time. The syntax is: hours, minutes, seconds, day, month, year.

Let's get the timestamp for 31.01.2017 12:43:59:

<?php
	echo mktime(12, 43, 59, 1, 31, 2017);
?>

The strtotime Function

The strtotime function is an analogue of the mktime function (it also returns a timestamp), but unlike it, accepts a date in a more flexible format. What else you can do: you can write like this - strtotime('now') - and we will get the current moment in time, or like this - strtotime('next Monday') - and we will get the next Monday (Monday in English 'понедельник'). See the example:

<?php
	echo strtotime('now');
	
	echo strtotime('10 September 2000');
	
	echo strtotime('+1 day');
	
	echo strtotime('+1 week');
	
	echo strtotime('+1 week 2 days 4 hours 2 seconds');
	
	echo strtotime('next Thursday');
	
	echo strtotime('last Monday');
?>