The DATE_*
  constants are defined and offer standard
  date representations, which can be used along with the date format functions
  (like date()).
 
returnFormat for
   date_sunrise() and
   date_sunset()
  
  These constants are deprecated as of PHP 8.4.0. The corresponding date_sunrise() and date_sunset() functions are deprecated as of PHP 8.1.0.
SUNFUNCS_RET_TIMESTAMP
    (int)
   SUNFUNCS_RET_STRING
    (int)
   08:02)
    
   SUNFUNCS_RET_DOUBLE
    (int)
   8.75)
    
   DATE_* constants
  
   DATE_ATOM
    (string)
   2005-08-15T15:52:01+00:00)
    
   Monday, 15-Aug-2005 15:52:01 UTC)
    
   DATE_ISO8601
    (string)
   2005-08-15T15:52:01+0000)
    
    Note: This format is not compatible with ISO-8601, but is left this way for backward compatibility reasons. Use
DATE_ISO8601_EXPANDED,DATE_ATOMfor compatibility with ISO-8601 instead (ref ISO8601:2004 section 4.3.3 clause d).
DATE_ISO8601_EXPANDED
    (string)
   +10191-07-26T08:59:52+01:00)
    
    Note: This format allows for year ranges outside of ISO-8601's normal range of
0000-9999by always including a sign character. It also ensures that the timezone part (+01:00) is compatible with ISO-8601.
DATE_RFC822
    (string)
   Mon, 15 Aug 05 15:52:01 +0000)
    
   DATE_RFC850
    (string)
   Monday, 15-Aug-05 15:52:01 UTC)
    
   DATE_RFC1036
    (string)
   Mon, 15 Aug 05 15:52:01 +0000)
    
   DATE_RFC1123
    (string)
   Mon, 15 Aug 2005 15:52:01 +0000)
    
   DATE_RFC7231
    (string)
   Sat, 30 Apr 2016 17:52:13 GMT)
    
   DATE_RFC2822
    (string)
   Mon, 15 Aug 2005 15:52:01 +0000)
    
   DATE_RFC3339
    (string)
   DATE_ATOM.
    
   DATE_RFC3339_EXTENDED
    (string)
   2005-08-15T15:52:01.000+00:00)
    
   DATE_RSS
    (string)
   Mon, 15 Aug 2005 15:52:01 +0000).
     Alias of DATE_RFC1123.
    
   DATE_W3C
    (string)
   2005-08-15T15:52:01+00:00).
     Alias of DATE_RFC3339.