Taken from: http://www.w3schools.com/php/func_date_date.asp

The date() function formats a local time/date.

Syntax

date(format,timestamp)

The timestamp is optional, format options are listed below:

Specifies how to format the result:

• d – The day of the month (from 01 to 31)
• D – A textual representation of a day (three letters)
• j – The day of the month without leading zeros (1 to 31)
• l (lowercase ‘L’) – A full textual representation of a day
• N – The ISO-8601 numeric representation of a day (1 for Monday through 7 for Sunday)
• S – The English ordinal suffix for the day of the month (2 characters st, nd, rd or th. Works well with j)
• w – A numeric representation of the day (0 for Sunday through 6 for Saturday)
• z – The day of the year (from 0 through 365)
• W – The ISO-8601 week number of year (weeks starting on Monday)
• F – A full textual representation of a month (January through December)
• m – A numeric representation of a month (from 01 to 12)
• M – A short textual representation of a month (three letters)
• n – A numeric representation of a month, without leading zeros (1 to 12)
• t – The number of days in the given month
• L – Whether it’s a leap year (1 if it is a leap year, 0 otherwise)
• o – The ISO-8601 year number
• Y – A four digit representation of a year
• y – A two digit representation of a year
• a – Lowercase am or pm
• A – Uppercase AM or PM
• B – Swatch Internet time (000 to 999)
• g – 12-hour format of an hour (1 to 12)
• G – 24-hour format of an hour (0 to 23)
• h – 12-hour format of an hour (01 to 12)
• H – 24-hour format of an hour (00 to 23)
• i – Minutes with leading zeros (00 to 59)
• s – Seconds, with leading zeros (00 to 59)
• e – The timezone identifier (Examples: UTC, Atlantic/Azores)
• I (capital i) – Whether the date is in daylights savings time (1 if Daylight Savings Time, 0 otherwise)
• O – Difference to Greenwich time (GMT) in hours (Example: +0100)
• T – Timezone setting of the PHP machine (Examples: EST, MDT)
• Z – Timezone offset in seconds. The offset west of UTC is negative, and the offset east of UTC is positive (-43200 to 43200)
• c – The ISO-8601 date (e.g. 2004-02-12T15:19:21+00:00)
• r – The RFC 2822 formatted date (e.g. Thu, 21 Dec 2000 16:01:07 +0200)
• U – The seconds since the Unix Epoch (January 1 1970 00:00:00 GMT)

<?php
echo("Result with date():<br />");
echo(date("l") . "<br />");
echo(date("l dS \of F Y h:i:s A") . "<br />");
echo("Oct 3,1975 was on a ".date("l", mktime(0,0,0,10,3,1975))."<br />");
echo(date(DATE_RFC822) . "<br />");
echo(date(DATE_ATOM,mktime(0,0,0,10,3,1975)) . "<br /><br />");

echo("Result with gmdate():<br />");
echo(gmdate("l") . "<br />");
echo(gmdate("l dS \of F Y h:i:s A") . "<br />");
echo("Oct 3,1975 was on a ".gmdate("l", mktime(0,0,0,10,3,1975))."<br />");
echo(gmdate(DATE_RFC822) . "<br />");
echo(gmdate(DATE_ATOM,mktime(0,0,0,10,3,1975)) . "<br />");
?>

The output of the code above could be something like this:

Result with date():
Tuesday
Tuesday 24th of January 2006 02:41:22 PM
Oct 3,1975 was on a Friday
Tue, 24 Jan 2006 14:41:22 CET
1975-10-03T00:00:00+0100

Result with gmdate():
Tuesday
Tuesday 24th of January 2006 01:41:22 PM
Oct 3,1975 was on a Thursday
Tue, 24 Jan 2006 13:41:22 GMT
1975-10-02T23:00:00+0000