Specifies the format of the outputted date string. The following characters can be used:
- 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, 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, 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)
- u – Microseconds (added in PHP 5.2.2)
- e – The timezone identifier (Examples: UTC, GMT, 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)
- P – Difference to Greenwich time (GMT) in hours:minutes (added in PHP 5.1.3)
- T – Timezone abbreviations (Examples: EST, MDT)
- Z – Timezone offset in seconds. The offset for timezones west of UTC is negative (-43200 to 50400)
- c – The ISO-8601 date (e.g. 2013-05-05T16:34:42+00:00)
- r – The RFC 2822 formatted date (e.g. Fri, 12 Apr 2013 12:01:05 +0200)
- U – The seconds since the Unix Epoch (January 1 1970 00:00:00 GMT)
