Formato Data e Hora no PHP

echo date(DateTime::W3C); // 2005-08-15T15:52:01+00:00

Lista de formatos:

ATOM = “Y-m-d\TH:i:sP” ; // -> 2005-08-15T15:52:01+00:00
COOKIE = “l, d-M-Y H:i:s T” ; // -> Monday, 15-Aug-2005 15:52:01 UTC
ISO8601 = “Y-m-d\TH:i:sO” ; // -> 2005-08-15T15:52:01+0000
RFC822 = “D, d M y H:i:s O” ; // -> Mon, 15 Aug 05 15:52:01 +0000
RFC850 = “l, d-M-y H:i:s T” ; // -> Monday, 15-Aug-05 15:52:01 UTC
RFC1036 = “D, d M y H:i:s O” ; // -> Mon, 15 Aug 05 15:52:01 +0000
RFC1123 = “D, d M Y H:i:s O” ; // -> Mon, 15 Aug 2005 15:52:01 +0000
RFC2822 = “D, d M Y H:i:s O” ; // -> Mon, 15 Aug 2005 15:52:01 +0000
RFC3339 = “Y-m-d\TH:i:sP” ; // -> 2005-08-15T15:52:01+00:00 ( == ATOM)
RFC3339_EXTENDED = “Y-m-d\TH:i:s.vP” ; // -> 2005-08-15T15:52:01.000+00:00
RSS = “D, d M Y H:i:s O” ; // -> Mon, 15 Aug 2005 15:52:01 +0000
W3C = “Y-m-d\TH:i:sP” ; // -> 2005-08-15T15:52:01+00:00