System.now() gives a different hour value and System.now().hour() gives a different value. can any one tell me why so?

Question

String day = string.valueOf(system.now().day());
String month = string.valueOf(system.now().month());
String hour = string.valueOf(system.now().hour());
String minute = string.valueOf(system.now().minute());
String second = string.valueOf(system.now().second());
String year = string.valueOf(system.now().year());

String strTime = year+'-'+month+'-'+day+' '+hour+':'+minute+':'+second ;

system.debug(strTime);
system.debug(system.now());

output 1: 2015-7-7 14:5:55

output 2: 2015-07-07 08:35:55

================================================

Answer 1

DateTime objects have built-in support for the user's timezone. So DateTime.hour:

Returns the hour component of a Datetime in the local time zone of the context user.

DateTime.format also includes the timezone offset but just doing a default DateTime conversion to a string looks like it presents the underlying GMT value.

Answer 2

System.now() returns the DateTime in GMT time zone, whereas System.now().hour() is the method of DateTime class, which returns the local time zone of the context user.