delphi - How to avoid TDateTime Data Rounding -

i writing column , cell classes fmx tgrid contain tcalendaredit , ttimeedit instances in every cell. works fine except proper processing of changes done in these child controls.

type   tfmtvalue<t> = record     fieldvalue: t;     modified: boolean;     appended: boolean;     deleted: boolean;   end;    tdatetimecell = class(tstyledcontrol)     private       fdate_time: tfmtvalue<tdatetime>;       procedure setdatetime(const value: tfmtvalue<tdatetime>);       function getdatetime: tfmtvalue<tdatetime>;     protected       procedure setdata(const value: tvalue); override;     public       property date_time: tfmtvalue<tdatetime> read getdatetime write setdatetime;     ...       end; ...        function tdatetimecell.getdatetime: tfmtvalue<tdatetime>;     begin       fdate_time.modified := (fdate_time.modified) or         (fdate_time.fieldvalue <> fcalendaredit.date +          + ftimeedit.time);       fdate_time.fieldvalue := fcalendaredit.date + ftimeedit.time;       result := fdate_time;     end;      procedure tdatetimecell.setdata(const value: tvalue);     begin       date_time := value.astype<tfmtvalue<tdatetime>>;       inherited setdata(tvalue.from<tdatetime>(fdate_time.fieldvalue));       applystyling;     end;      procedure tdatetimecell.setdatetime(const value: tfmtvalue<tdatetime>);     begin       fdate_time := value;       fcalendaredit.date := dateof(fdate_time.fieldvalue);       ftimeedit.time := timeof(fdate_time.fieldvalue);       fdate_time.fieldvalue:=fcalendaredit.date + ftimeedit.time; //this line helps not in cases     end; 

the idea data assigned via tgrid ongetvalue event handler. both date , time displayed. user activity catched , modified flag set. problem flag set true without user activities. suspect due rounding of time part of tdatetime. there no other ways code assignes values fcalendaredit.date , ftimeedit.time.

how can compare data stored in fcalendaredit.date , ftimeedit.time stored in fdate_time.fieldvalue?

appended

setting flag in way not resolve issue.

  fdate_time.modified := (fdate_time.modified) or     (dateof(fdate_time.fieldvalue) <> fcalendaredit.date) or     (timeof(fdate_time.fieldvalue)<> ftimeedit.time); 

appended 2. on valued advice of @ken-white. if replace comparison line by

fdate_time.modified := (fdate_time.modified) or (not samedatetime(fdate_time.fieldvalue,  fcalendaredit.date + ftimeedit.time)); 

it works fine. tdatatime comparison must done function only.

tdatetime of type double, means it's floating point value, , therefore subject usual issues of binary representation when doing comparisons equality without specifying acceptable delta (difference)..

specifically tdatetime values, can use dateutils.samedatetime compare equality down less 1 millisecond:

fdate_time.modified := (fdate_time.modified) or            (not samedatetime(fdate_time.fieldvalue,              fcalendaredit.date + ftimeedit.time));