php time format

1$today = date("F j, Y, g:i a");   // October 30, 2019, 10:42 pm
2$today = date("D M j G:i:s T Y"); // Wed Oct 30 22:42:18 UTC 2019
3$today = date("Y-m-d H:i:s");     // 2019-10-30 22:42:18(MySQL DATETIME format)

1<?php
2// Assuming today is March 10th, 2001, 5:16:18 pm, and that we are in the
3// Mountain Standard Time (MST) Time Zone
4//
5$today = date("F j, Y, g:i a");                 // March 10, 2001, 5:16 pm
6$today = date("m.d.y");                         // 03.10.01
7$today = date("j, n, Y");                       // 10, 3, 2001
8$today = date("Ymd");                           // 20010310
9$today = date('h-i-s, j-m-y, it is w Day');     // 05-16-18, 10-03-01, 1631 1618 6 Satpm01
10$today = date('\i\t \i\s \t\h\e jS \d\a\y.');   // it is the 10th day.
11$today = date("D M j G:i:s T Y");               // Sat Mar 10 17:16:18 MST 2001
12$today = date('H:m:s \m \i\s\ \m\o\n\t\h');     // 17:03:18 m is month
13$today = date("H:i:s");                         // 17:16:18
14$today = date("Y-m-d H:i:s");                   // 2001-03-10 17:16:18 (the MySQL DATETIME format)
15?>
16  
17/*d	Day of the month, 2 digits with leading zeros	01 to 31
18D	A textual representation of a day, three letters	Mon through Sun
19j	Day of the month without leading zeros	1 to 31
20l (lowercase 'L')	A full textual representation of the day of the week	Sunday through Saturday
21N	ISO-8601 numeric representation of the day of the week (added in PHP 5.1.0)	1 (for Monday) through 7 (for Sunday)
22S	English ordinal suffix for the day of the month, 2 characters	st, nd, rd or th. Works well with j
23w	Numeric representation of the day of the week	0 (for Sunday) through 6 (for Saturday)
24z	The day of the year (starting from 0)	0 through 365
25Week	---	---
26W	ISO-8601 week number of year, weeks starting on Monday	Example: 42 (the 42nd week in the year)
27Month	---	---
28F	A full textual representation of a month, such as January or March	January through December
29m	Numeric representation of a month, with leading zeros	01 through 12
30M	A short textual representation of a month, three letters	Jan through Dec
31n	Numeric representation of a month, without leading zeros	1 through 12
32t	Number of days in the given month	28 through 31
33Year	---	---
34L	Whether it's a leap year	1 if it is a leap year, 0 otherwise.
35o	ISO-8601 week-numbering year. This has the same value as Y, except that if the ISO week number (W) belongs to the previous or next year, that year is used instead. (added in PHP 5.1.0)	Examples: 1999 or 2003
36Y	A full numeric representation of a year, 4 digits	Examples: 1999 or 2003
37y	A two digit representation of a year	Examples: 99 or 03
38Time	---	---
39a	Lowercase Ante meridiem and Post meridiem	am or pm
40A	Uppercase Ante meridiem and Post meridiem	AM or PM
41B	Swatch Internet time	000 through 999
42g	12-hour format of an hour without leading zeros	1 through 12
43G	24-hour format of an hour without leading zeros	0 through 23
44h	12-hour format of an hour with leading zeros	01 through 12
45H	24-hour format of an hour with leading zeros	00 through 23
46i	Minutes with leading zeros	00 to 59
47s	Seconds with leading zeros	00 through 59
48u	Microseconds (added in PHP 5.2.2). Note that date() will always generate 000000 since it takes an integer parameter, whereas DateTime::format() does support microseconds if DateTime was created with microseconds.	Example: 654321
49v	Milliseconds (added in PHP 7.0.0). Same note applies as for u.	Example: 654
50Timezone	---	---
51e	Timezone identifier (added in PHP 5.1.0)	Examples: UTC, GMT, Atlantic/Azores
52I (capital i)	Whether or not the date is in daylight saving time	1 if Daylight Saving Time, 0 otherwise.
53O	Difference to Greenwich time (GMT) without colon between hours and minutes	Example: +0200
54P	Difference to Greenwich time (GMT) with colon between hours and minutes (added in PHP 5.1.3)	Example: +02:00
55T	Timezone abbreviation	Examples: EST, MDT ...
56Z	Timezone offset in seconds. The offset for timezones west of UTC is always negative, and for those east of UTC is always positive.	-43200 through 50400
57Full Date/Time	---	---
58c	ISO 8601 date (added in PHP 5)	2004-02-12T15:19:21+00:00
59r	» RFC 2822 formatted date	Example: Thu, 21 Dec 2000 16:01:07 +0200
60U	Seconds since the Unix Epoch (January 1 1970 00:00:00 GMT)	See also time()
61*/

1$today = date("F j, Y, g:i a");               // March 10, 2001, 5:16 pm
2$today = date("m.d.y");                       // 03.10.01
3$today = date("j, n, Y");                     // 10, 3, 2001
4$today = date("Ymd");                         // 20010310
5$today = date('h-i-s, j-m-y, it is w Day');   // 05-16-18, 10-03-01, 1631 1618 6 Satpm01
6$today = date('\i\t \i\s \t\h\e jS \d\a\y.'); // it is the 10th day.
7$today = date("D M j G:i:s T Y");             // Sat Mar 10 17:16:18 MST 2001
8$today = date('H:m:s \m \i\s\ \m\o\n\t\h');   // 17:03:18 m is month
9$today = date("H:i:s");                       // 17:16:18
10$today = date("Y-m-d H:i:s");                 // 2001-03-10 17:16:18 (the MySQL DATETIME format)
11

1<?php
2  // To change the format of an existing date
3  $old_date_format = "20/03/1999";
4  $new_data_format = date("Y-m-d H:i:s", strtotime($old_date_format));

1$originalDate = "2017-03-08";
2$newDate = date("d/m/Y", strtotime($originalDate));
3

1<?php
2  	$date = '05/05/2021';
3	echo DateTime::createFromFormat("d/m/Y", $date)->format('Y-m-d');
4	//2021-05-05
5