Why data of timestamptz does not store value of timezone passed to it?

<div dir="ltr">Hi,all<br />  <br /> I have a question about data type "timestamp with time zone".<br />Why data of
timestamptzdoes not store value of timezone passed to it?<br /><br />Considering the following example.<br />  <br />
postgres=#select '2014-08-28 14:30:30.423602+02'::timestamp with time zone;<br />          timestamptz          <br
/>-------------------------------<br/> 2014-08-28 20:30:30.423602+08<br />(1 row)<br />  <br /> The timezone of
output(+08)is different with the original input value(+02).<br />It seems not to be good behavior.But the behavior of
datetype "time with time zone" is correct.<br />  <br /> postgres=# select '14:30:30.423602+02'::time with time
zone;<br/>       timetz       <br />--------------------<br /> 14:30:30.423602+02<br />(1 row)<br />  <br /> If the
correntbehavior of timestamptz is not suitable,is there any plan to correct the behavior of timestamptz or create a new
datatype which can store timestamp with timezone?<br />  <br /><br />*）manual-->8.5.1.3. Time Stamps<br
/>---------------------------------------------------------<br/>For timestamp with time zone, the internally stored
valueis always in UTC (Universal Coordinated Time, traditionally known as Greenwich Mean Time, GMT). An input value
thathas an explicit time zone specified is converted to UTC using the appropriate offset for that time zone. If no time
zoneis stated in the input string, then it is assumed to be in the time zone indicated by the system's TimeZone
parameter,and is converted to UTC using the offset for the timezone zone.<br
/>---------------------------------------------------------<br/>  <br />  <br />  <br /> Best regarts<br /> rohto<br />
 <br/>  <br />  <br />  <br />  <br /> rohto<br /></div>