Here is my source XML:

<Chat>
        <Chat StartTime="2017-05-28T02:05:52"> 
            <message userId="02A0592964A8F75F" timeShift="4">
                <msgText> Hi </msgText> 
             </message>
             <message userId="123458566666666B"  timeShift="30"> 
            <msgText> Hello.. How can I Help You. ? </msgText> 
            </message
</Chat>

I need an XSL to trnsform the source as:

 <Chats>
     <message time="2017-05-28T02:05:56" userId="02A0592964A8F75F">Hi</message>
     <message time="2017-05-28T02:06:32" userId="02A0592964A8F75F">Hello.. How can I Help You. ?</message> 
 </Chats>

In the output XML file, message time should be updated with the StartTime based on TimeShift(seconds).

Please kindly help me to get this.
Thanks in advance.