Add Time to a TDateTime - delphi

Question

I would like to add seconds to a TDateTime variable, so that the result is the top of the minute. For example, if it's 08:30:25, I want change the TDateTime variable to store 08:31:00.
I see that TDateTime has a Decode function, which I could use. There isn't, however, an encode function to put the altered time back into a TDateTime variable.

Answer 1

Using DateUtils it's possible to do it like this:
Uses
DateUtils;
var
Seconds : Word;
Seconds := SecondOfTheMinute(MyTime); // Seconds from last whole minute
// Seconds := SecondOf(MyTime); is equivalent to SecondOfTheMinute()
if (Seconds > 0) then
MyTime := IncSecond(MyTime,60 - Seconds);

Answer 2

There sure is, at least in the recent versions - see the DateUtils unit, especially all the Recode* routines and EncodeDateTime. The DateUtils unit is already available in Delphi 2010, perhaps even in earlier version.

Answer 3

Theory
The TDateTime data type represents number of days since 30 Dec 1899 as a real number. That is, the integral part of TDateTime is an amount of whole days, and the fractional part represents a time of day.
Practical
Therefore, your problem could be solved using simple arithmetics:
var
Days: TDateTime;
Mins: Extended; { widen TDateTime's mantissa by 11 bits to accommodate division error }
begin
Days := Date + StrToTime('08:30:25');
Writeln(DateTimeToStr(Days));
Mins := Days * 24 * 60 ; // compute minutes
Mins := Math.Ceil(Mins); // round them up
Days := Mins / (24 * 60); // and back to days
{ or as simple and concise expression as: }
// Days := Ceil(Days * MinsPerDay) / MinsPerDay;
Writeln(DateTimeToStr(Days));