TimeZonePreference property doen't work with search from Grid

I have a grid with a column of UTCDateTime type, and the values in the data source table are already converted into local time. I set the TimeZonePreference  = 'No Conversion' so that the grid will populate local date time correctly without automatically conversion, but when I search date range (ctrl+g), it shows unexpected result - the result is based on UTC datetime. It converted before comparing! checked all properties, I can't find one to resolve this.  Thanks in advance.