Something i found from Wiki. Please look into this it can help how to convert time zones

1. 1. //converting GMT to Canada/Eastern  
   1. 2.  
2. 3. var tz = Packages.java.util.TimeZone.getTimeZone("Canada/Eastern");  
   1. 4. gDate.setTZ(tz);  

...right after you initialize the variable and before you assign the date to it.     You should end up with:

1. 1. var gDate = Packages.com.glide.glideobject.GlideDateTime();  
   1. 2. //converting GMT to Canada/Eastern  
2. 3.  
   1. 4. var tz = Packages.java.util.TimeZone.getTimeZone("Canada/Eastern");  
3. 5. gDate.setTZ(tz);  
   1. 6. gDate.setValue(msDate);