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Developer Forum » Software Engineering and Information Technology » Delphi » Converts a date or time or date+time string into a TDateTime value in Delphi

Converts a date or time or date+time string into a TDateTime value in Delphi Options · View
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hong
Posted: Sunday, June 21, 2009 2:27:36 PM

Rank: Administration
Groups: Administration

Joined: 11/23/2008
Posts: 335
Points: 711
Location: Australia
Converts a date or time or date+time string into a TDateTime value in Delphi

StrToDateTime Converts a date+time string into a TDateTime value
1 function StrToDateTime ( const DateTime : string ) : TDateTime;
2 function StrToDateTime ( const DateTime : string; const FormatSettings : TFormatSettings ) : TDateTime;
Code:
  myDateTime := StrToDateTime('21/06/09 17');
  myDateTime := StrToDateTime('21/06/09 16:48:23');


String DateTime -> TDateTime myDateTime
-----------------------------------------
21/06/09 17 -> 21/06/09 17:00:00
21/06/09 16:48:23 -> 21/06/09 16:48:23

StrToDate Converts a date string into a TDateTime value
1 function StrToDate ( const Date : string ) : TDateTime;
2 function StrToDate ( const Date : string; const FormatSettings : TFormatSettings ) : TDateTime;

Code:
  myDate := StrToDate('18/06/09');
  myDate := StrToDate('18/06/09');



StrToTime Converts a time string into a TDateTime value
1 function StrToTime ( const Time : string ) : TDateTime;
2 function StrToTime ( const Time : string; const FormatSettings : TFormatSettings ) : TDateTime;

Code:
  myTime := StrToTime('9PM');
  myTime := StrToTime('21');
  myTime := StrToTime('21:01');
  myTime := StrToTime('21:01:01');



String Time -> TDateTime myTime
-----------------------------------------
9PM -> 21:00:00
21 -> 21:00:00
21:01 -> 21:01:00
21:01:01 -> 21:01:01


The following function ConvertToDateTime also converts a date string in DDMMYYYY format to a TDateTime
An exception is thrown on an invalid format.
Code:
function ConvertToDateTime(const strDate : String): TDateTime;
var
  strDay, strMonth, strYear: Word;
begin
  strDay := StrToInt(Copy(strDate, 1, 2));
  strMonth := StrToInt(Copy(strDate, 3, 2));
  strYear := StrToInt(Copy(strDate, 5, 4));
  Result := EncodeDate(strYear, strMonth, strDay);
end;

function IsValidDate(const strDate : String): Boolean;
begin
  Result := True;
  try
    ConvertToDateTime(strDate);
  except
    Result := False;
  end;
end;
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Sponsor
Posted: Sunday, June 21, 2009 2:27:36 PM
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hong
Posted: Sunday, June 21, 2009 2:34:41 PM

Rank: Administration
Groups: Administration

Joined: 11/23/2008
Posts: 335
Points: 711
Location: Australia
Date and Time Format in Delphi

y = Year last 2 digits
yy = Year last 2 digits
yyyy = Year as 4 digits
m = Month number no-leading 0
mm = Month number as 2 digits
mmm = Month using ShortDayNames (Jan)
mmmm = Month using LongDayNames (January)
d = Day number no-leading 0
dd = Day number as 2 digits
ddd = Day using ShortDayNames (Sun)
dddd = Day using LongDayNames (Sunday)
ddddd = Day in ShortDateFormat
dddddd = Day in LongDateFormat

c = Use ShortDateFormat + LongTimeFormat
h = Hour number no-leading 0
hh = Hour number as 2 digits
n = Minute number no-leading 0
nn = Minute number as 2 digits
s = Second number no-leading 0
ss = Second number as 2 digits
z = Milli-sec number no-leading 0s
zzz = Milli-sec number as 3 digits
t = Use ShortTimeFormat
tt = Use LongTimeFormat

am/pm = Use after h : gives 12 hours + am/pm
a/p = Use after h : gives 12 hours + a/p
ampm = As a/p but TimeAMString,TimePMString
/ = Substituted by DateSeparator value
: = Substituted by TimeSeparator value


DateSeparator = /
TimeSeparator = :
ShortDateFormat = dd/mm/yyyy
LongDateFormat = dd mmm yyyy
TimeAMString = AM
TimePMString = PM
ShortTimeFormat = hh:mm
LongTimeFormat = hh:mm:ss
ShortMonthNames = Jan Feb ...
LongMonthNames = January, February ...
ShortDayNames = Sun, Mon ...
LongDayNames = Sunday, Monday ...
TwoDigitYearCenturyWindow = 50

The default format in Australia is day/month/year, eg. '21/6/2009'.
MyDateTime : TDateTime = StrToDate('21/6/2009');
To change the date format from '6-21-2009' to '21/6/2009':
Code:
strInstallationDate := '6-21-2009';         
DateSeparator := '-';
          ShortDateFormat := 'd-m-yyyy';
          try
            MyDateTime := StrToDate(strInstallationDate);
            result := InstallationDate;
          except
            bValidDate := false;
          end;
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