Expired / time interval in Delphi?

Question

I need to calculate the elapsed time (beautifully formatted) between now and the last change in the file date / time , i.e., something like this , only in my case the difference can be in days, months or even years.

I tried this:

var TimeDiff : Double; begin TimeDiff := Now - FileAgeEx('C:\my-file.txt'); if (TimeDiff >= 1) then Caption := FormatDateTime('dd hh:nn:ss', TimeDiff) else Caption := FormatDateTime('hh:nn:ss', TimeDiff); end; 

But (1) it does not work and (2) I would like to format it better.

Ultimately, my goal is to have something like this:

• Diff time <1 day ==> show this: 12:00:01
• Diff time> = 1 day ==> displays this: 25 days, 12:00:01
• Diff time> = 1 year ==> it displays: 2 years, 3 months, 10 days, 12:00:01

Does anyone know how I can do this?

Thanks!

Answer 1

The main problem, apparently, is getting the last modified file time. I am using the following code:

 function LastWriteTime(const FileName: string): TFileTime; var AttributeData: TWin32FileAttributeData; begin if not GetFileAttributesEx(PChar(FileName), GetFileExInfoStandard, @AttributeData) then RaiseLastOSError; Result := AttributeData.ftLastWriteTime; end; function UTCFileTimeToSystemTime(const FileTime: TFileTime): TSystemTime; //returns equivalent time in current locality, taking account of daylight saving var LocalFileTime: Windows.TFileTime; begin Windows.FileTimeToLocalFileTime(FileTime, LocalFileTime); Windows.FileTimeToSystemTime(LocalFileTime, Result); end; function UTCFileTimeToDateTime(const FileTime: TFileTime): TDateTime; begin Result := SystemTimeToDateTime(UTCFileTimeToSystemTime(FileTime)); end; 

You call LastWriteTime to get the last modified time in a time file format. Then call UTCFileTimeToDateTime to convert to TDateTime , taking into account the prevailing local machine time zone. Then you can compare this value with Now .

As for formatting, you already know how to do it. Your basic approach will work, and you just need to find out the details.

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In the comments you say that

 FormatDateTime('dd hh:nn:ss', 2.9); 

shows a 1 for the day you expect a 2 . The problem is that this function formats dates, not time intervals. A value of 2.9 not considered elapsed time; rather, it is considered as an absolute date / time, 2.9 days after the Delphi era. I would use Trunc and Frac to get the number of days and part of the days respectively and work from there.

 Days := Trunc(TimeDiff); Time := Frac(TimeDiff); 

The following code, extracted directly from my code base, can give you a few pointers. Note that its input is in seconds, but it should set you on the right path.

 function CorrectPlural(const s: string; Count: Integer): string; begin Result := IntToStr(Count) + ' ' + s; if Count<>1 then begin Result := Result + 's'; end; end; function HumanReadableTime(Time: Double): string; //Time is in seconds const SecondsPerMinute = 60; SecondsPerHour = 60*SecondsPerMinute; SecondsPerDay = 24*SecondsPerHour; SecondsPerWeek = 7*SecondsPerDay; SecondsPerYear = 365*SecondsPerDay; var Years, Weeks, Days, Hours, Minutes, Seconds: Int64; begin Try Years := Trunc(Time/SecondsPerYear); Time := Time - Years*SecondsPerYear; Weeks := Trunc(Time/SecondsPerWeek); Time := Time - Weeks*SecondsPerWeek; Days := Trunc(Time/SecondsPerDay); Time := Time - Days*SecondsPerDay; Hours := Trunc(Time/SecondsPerHour); Time := Time - Hours*SecondsPerHour; Minutes := Trunc(Time/SecondsPerMinute); Time := Time - Minutes*SecondsPerMinute; Seconds := Trunc(Time); if Years>5000 then begin Result := IntToStr(Round(Years/1000))+' millennia'; end else if Years>500 then begin Result := IntToStr(Round(Years/100))+' centuries'; end else if Years>0 then begin Result := CorrectPlural('year', Years) + ' ' + CorrectPlural('week', Weeks); end else if Weeks>0 then begin Result := CorrectPlural('week', Weeks) + ' ' + CorrectPlural('day', Days); end else if Days>0 then begin Result := CorrectPlural('day', Days) + ' ' + CorrectPlural('hour', Hours); end else if Hours>0 then begin Result := CorrectPlural('hour', Hours) + ' ' + CorrectPlural('minute', Minutes); end else if Minutes>0 then begin Result := CorrectPlural('minute', Minutes); end else begin Result := CorrectPlural('second', Seconds); end; Except Result := 'an eternity'; End; end;