Unix Timestamp (Seconds since epoch)  
t  =  Time . now 
# => 2012-11-05 11:12:25 -0500 
t . to_i 
# => 1352131945 
tu  =  t . utc 
# => 2012-11-05 16:12:25 UTC 
tu . to_i 
# => 1352131945  
php > date_default_timezone_set ("UTC " );
php > $ t  = new  DateTime ("@1352131945 " );
php > echo date_format ($ t , "Y-m-d H:i:s " );
2012 -11 -05  16 :12 :25 
php > echo date_format ($ t , "Y-m-d H:i:s e " );
2012 -11 -05  16 :12 :25  +00 :00 
php > $ t ->setTimezone (new  DateTimeZone ("America/New_York " ));
php > echo date_format ($ t , "Y-m-d H:i:s e " );
2012 -11 -05  11 :12 :25  America/New_York  
Generating from Ruby (w/ ActiveSupport)  
>> t  =  Time . now 
=>  Mon  Nov  05  11 :39 :09  -0500  2012 
>> tu  =  t . utc 
=>  Mon  Nov  05  16 :39 :09  UTC  2012  
>> t . to_s ( :rfc822 )  
=>  "Mon, 05 Nov 2012 16:39:09 +0000"  
>> tu . to_s ( :rfc822 ) 
=>  "Mon, 05 Nov 2012 16:39:09 +0000"   
irb ( main ) :001 :0 > require  'time' 
=>  true 
irb ( main ) :002 :0 > t  =  Time . parse ( "Mon, 05 Nov 2012 16:39:09 +0000" ) 
=>  2012 -11 -05  11 :39 :09  -0500  
php > date_default_timezone_set ("UTC " );
php > $ t  = new  DateTime ("Mon, 05 Nov 2012 16:39:09 +0000 " );
php > echo date_format ($ t , "Y-m-d H:i:s " );
2012 -11 -05  16 :39 :0 9 
php > echo date_format ($ t , "Y-m-d H:i:s e " );
2012 -11 -05  16 :39 :0 9  +00 :00 
php > $ t ->setTimezone (new  DateTimeZone ("America/New_York " ));
php > echo date_format ($ t , "Y-m-d H:i:s e " );
2012 -11 -05  11 :39 :0 9  America/New_York