Round TTime to nearest 15 minutes - delphi

Question

I have the following function which I'm led to believe should round time to nearest 15 minutes.
function TdmData.RoundTime(T: TTime): TTime;
var h, m, s, ms : Word;
begin
DecodeTime(T, h, m, s, ms);
m := (m div 15) * 15;
s := 0;
Result := EncodeTime(h, m, s, ms);
end;
To test the function I have put a tbutton and a tedit on a form and at the click of the button I do:
begin
Edit1.Text := RoundTime('12:08:27');
end;
I get an error when compiling : 'Incompatible types TTime and string'
Any help with this would be great.
Thanks,

Answer 1

The error which causes the compilation failure is that you are passing a string to a function which needs a TTime as a parameter.
Once this is fixed, Edit1.Text needs a string type but your function returns TTime.
Using StrToTime and TimeToStr you can obtain the desired conversion from and to a string type.
Your function can be called like this:
begin
Edit1.Text := TimeToStr(RoundTime(StrToTime('12:08:27'));
end;
Stealing the gabr user's answer - In Delphi: How do I round a TDateTime to closest second, minute, five-minute etc? - you can obtain a date rounded to an arbitrary nearest value assigned to the interval parameter:
function RoundToNearest(time, interval: TDateTime): TDateTime;
var
time_sec, int_sec, rounded_sec: int64;
begin
time_sec := Round(time * SecsPerDay);
int_sec := Round(interval * SecsPerDay);
rounded_sec := (time_sec div int_sec) * int_sec;
if ((rounded_sec + int_sec - time_sec) - (time_sec - rounded_sec)) > 0 then
rounded_sec := rounded_sec + time_sec + int_sec;
Result := rounded_sec / SecsPerDay;
end;
begin
Edit1.Text := TimeToStr(RoundToNearest(StrToTime('12:08:27'), StrToTime('0:0:15')));
end;