数式を使った時にGMTになるのをローカルタイムに変更したい

Flowでも問題だけど、数式で使えないかな？ <--- 最終的には数式で逃げたような感じです。

Simple question, should be easy for you geniuses! Displaying Date/Time in Flow

CASE( MOD(  DATEVALUE({!YOURDATETIMEFIELD__c} ) - DATE(1900, 1, 7), 7), 
0, "Sunday", 
1, "Monday", 
2, "Tuesday", 
3, "Wednesday", 
4, "Thursday", 
5, "Friday", 
6, "Saturday", 
"Error") 
& ", " &  
CASE(MONTH(DATEVALUE({!YOURDATETIMEFIELD__c})),  
1, "January",  
2, "February",  
3, "March",  
4, "April",  
5, "May",  
6, "June",  
7, "July",  
8, "August",  
9, "September",  
10, "October",  
11, "November",  
12, "December",  
"None"  )
& " " &  

TEXT(DAY( DATEVALUE({!YOURDATETIMEFIELD__c}))) 
& ", " & 
TEXT(YEAR(DATEVALUE({!YOURDATETIMEFIELD__c})))  
& " at " & 
TEXT(IF( OR( VALUE( MID( TEXT( {!YOURDATETIMEFIELD__c} 

+ $Setup.Custom_Settings__c.Time_Zone_GMT__c/24 ), 12, 2 ) ) = 0, VALUE( MID( TEXT( {!YOURDATETIMEFIELD__c} +  $Setup.Custom_Settings__c.Time_Zone_GMT__c/24  ), 12, 2 ) ) = 12 ), 12, VALUE( MID( TEXT( {!YOURDATETIMEFIELD__c}  + $Setup.Custom_Settings__c.Time_Zone_GMT__c/24 ), 12, 2 ) ) - IF( VALUE( MID( TEXT( {!YOURDATETIMEFIELD__c} 

+ $Setup.Custom_Settings__c.Time_Zone_GMT__c/24 ), 12, 2 ) ) < 12, 0, 12 ) )) & ":" & MID( TEXT(  {!YOURDATETIMEFIELD__c} 

+ $Setup.Custom_Settings__c.Time_Zone_GMT__c/24 ), 15, 2 ) & " " & IF( VALUE( MID( TEXT(  {!YOURDATETIMEFIELD__c} 

+ $Setup.Custom_Settings__c.Time_Zone_GMT__c/24), 12, 2 ) ) < 12, "am", "pm" )