?php
setlocale(LC_TIME, "C");
echo strftime("%A");
setlocale(LC_TIME, "fi_FI");
echo strftime(" in Finnish is %A,");
setlocale(LC_TIME, "fr_FR");
echo strftime(" in French %A and");
setlocale(LC_TIME, "de_DE");
echo strftime(" in German %A.\n");
?>

?php
/*   December 2002 / January 2003
ISOWk M  Tu W  Thu F  Sa Su
----- ----------------------------
51   16 17 18 19 20 21 22
52   23 24 25 26 27 28 29
1   30 31  1  2  3  4  5
2    6  7  8  9 10 11 12
3   13 14 15 16 17 18 19  */

// Outputs: 12/28/2002 - %V,%G,%Y = 52,2002,2002
echo "12/28/2002 - %V,%G,%Y = " . strftime("%V,%G,%Y", strtotime("12/28/2002")) . "\n";

// Outputs: 12/30/2002 - %V,%G,%Y = 1,2003,2002
echo "12/30/2002 - %V,%G,%Y = " . strftime("%V,%G,%Y", strtotime("12/30/2002")) . "\n";

// Outputs: 1/3/2003 - %V,%G,%Y = 1,2003,2003
echo "1/3/2003 - %V,%G,%Y = " . strftime("%V,%G,%Y",strtotime("1/3/2003")) . "\n";

// Outputs: 1/10/2003 - %V,%G,%Y = 2,2003,2003
echo "1/10/2003 - %V,%G,%Y = " . strftime("%V,%G,%Y",strtotime("1/10/2003")) . "\n";



/*   December 2004 / January 2005
ISOWk M  Tu W  Thu F  Sa Su
----- ----------------------------
51   13 14 15 16 17 18 19
52   20 21 22 23 24 25 26
53   27 28 29 30 31  1  2
1    3  4  5  6  7  8  9
2   10 11 12 13 14 15 16  */

// Outputs: 12/23/2004 - %V,%G,%Y = 52,2004,2004
echo "12/23/2004 - %V,%G,%Y = " . strftime("%V,%G,%Y",strtotime("12/23/2004")) . "\n";

// Outputs: 12/31/2004 - %V,%G,%Y = 53,2004,2004
echo "12/31/2004 - %V,%G,%Y = " . strftime("%V,%G,%Y",strtotime("12/31/2004")) . "\n";

// Outputs: 1/2/2005 - %V,%G,%Y = 53,2004,2005
echo "1/2/2005 - %V,%G,%Y = " . strftime("%V,%G,%Y",strtotime("1/2/2005")) . "\n";

// Outputs: 1/3/2005 - %V,%G,%Y = 1,2005,2005
echo "1/3/2005 - %V,%G,%Y = " . strftime("%V,%G,%Y",strtotime("1/3/2005")) . "\n";

?>

?php

// Jan 1: results in: '%e%1%' (%%, e, %%, %e, %%)
$format = '%%e%%%e%%';

// Check for Windows to find and replace the %e 
// modifier correctly
if (strtoupper(substr(PHP_OS, 0, 3)) == 'WIN') {
  $format = preg_replace('#(?!%)((?:%%)*)%e#', '\1%#d', $format);
}

echo strftime($format);
?>

?php
// Describe the formats.
$strftimeFormats = array(
  'A' => 'A full textual representation of the day',
  'B' => 'Full month name, based on the locale',
  'C' => 'Two digit representation of the century (year divided by 100, truncated to an integer)',
  'D' => 'Same as "%m/%d/%y"',
  'E' => '',
  'F' => 'Same as "%Y-%m-%d"',
  'G' => 'The full four-digit version of %g',
  'H' => 'Two digit representation of the hour in 24-hour format',
  'I' => 'Two digit representation of the hour in 12-hour format',
  'J' => '',
  'K' => '',
  'L' => '',
  'M' => 'Two digit representation of the minute',
  'N' => '',
  'O' => '',
  'P' => 'lower-case "am" or "pm" based on the given time',
  'Q' => '',
  'R' => 'Same as "%H:%M"',
  'S' => 'Two digit representation of the second',
  'T' => 'Same as "%H:%M:%S"',
  'U' => 'Week number of the given year, starting with the first Sunday as the first week',
  'V' => 'ISO-8601:1988 week number of the given year, starting with the first week of the year with at least 4 weekdays, with Monday being the start of the week',
  'W' => 'A numeric representation of the week of the year, starting with the first Monday as the first week',
  'X' => 'Preferred time representation based on locale, without the date',
  'Y' => 'Four digit representation for the year',
  'Z' => 'The time zone offset/abbreviation option NOT given by %z (depends on operating system)',
  'a' => 'An abbreviated textual representation of the day',
  'b' => 'Abbreviated month name, based on the locale',
  'c' => 'Preferred date and time stamp based on local',
  'd' => 'Two-digit day of the month (with leading zeros)',
  'e' => 'Day of the month, with a space preceding single digits',
  'f' => '',
  'g' => 'Two digit representation of the year going by ISO-8601:1988 standards (see %V)',
  'h' => 'Abbreviated month name, based on the locale (an alias of %b)',
  'i' => '',
  'j' => 'Day of the year, 3 digits with leading zeros',
  'k' => 'Hour in 24-hour format, with a space preceding single digits',
  'l' => 'Hour in 12-hour format, with a space preceding single digits',
  'm' => 'Two digit representation of the month',
  'n' => 'A newline character ("\n")',
  'o' => '',
  'p' => 'UPPER-CASE "AM" or "PM" based on the given time',
  'q' => '',
  'r' => 'Same as "%I:%M:%S %p"',
  's' => 'Unix Epoch Time timestamp',
  't' => 'A Tab character ("\t")',
  'u' => 'ISO-8601 numeric representation of the day of the week',
  'v' => '',
  'w' => 'Numeric representation of the day of the week',
  'x' => 'Preferred date representation based on locale, without the time',
  'y' => 'Two digit representation of the year',
  'z' => 'Either the time zone offset from UTC or the abbreviation (depends on operating system)',
  '%' => 'A literal percentage character ("%")',
);

// Results.
$strftimeValues = array();

// Evaluate the formats whilst suppressing any errors.
foreach($strftimeFormats as $format => $description){
  if (False !== ($value = @strftime("%{$format}"))){
    $strftimeValues[$format] = $value;
  }
}

// Find the longest value.
$maxValueLength = 2 + max(array_map('strlen', $strftimeValues));

// Report known formats.
foreach($strftimeValues as $format => $value){
  echo "Known format  : '{$format}' = ", str_pad("'{$value}'", $maxValueLength), " ( {$strftimeFormats[$format]} )\n";
}

// Report unknown formats.
foreach(array_diff_key($strftimeFormats, $strftimeValues) as $format => $description){
  echo "Unknown format : '{$format}'  ", str_pad(' ', $maxValueLength), ($description ? " ( {$description} )" : ''), "\n";
}
?>

?php
echo '本年中的第·' . strftime('%W', strtotime('+2 week midnight -0 second')) . '·周';
?>

?php
echo "現在時間是：" . strftime('%d.%B %Y %H:%M:%S', time());
?>

?php
echo '日期時間格式化為:' . strftime('%d.%B %Y %H:%M:%S', strtotime('2018-10-15'));
?>