delphi FormatDateTime

 

 

FormatDateTime Function Rich formatting of a TDateTime variable into a string SysUtils unit

1  function FormatDateTime(const Formatting : string; DateTime : TDateTime) : string; 2  function FormatDateTime (const Formatting : string; DateTime : TDateTime; const FormatSettings : TFormatSettings)  : string;

 

Description The FormatDateTime function provides rich formatting of a TDateTime value DateTime into a string. Formatting is defined by the Formatting string.   The Formatting string can comprise a mix of ordinary characters (that are passed unchanged to the result string), and data formatting characters. This formatting is best explained by the example code.   The following (non-Asian) formatting character strings can be used in the Formatting string:   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   Important : if you want to see characters such as dd in the formatted output, placing them in " marks will stop them being interpreted as date or time elements.   In addition to this formatting, various of the above options are affected by the following variables, withe their default values :   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   Version 2 of this function is for use within threads. You furnish the FormatSettings record before invoking the call. It takes a local copy of global formatting variables that make the routine thread safe.   Related commands DateSeparator   The character used to separate display date fields DateTimeToStr   Converts TDateTime date and time values to a string DateTimeToString   Rich formatting of a TDateTime variable into a string LongDateFormat   Long version of the date to string format LongDayNames   An array of days of the week names, starting 1 = Sunday LongMonthNames   An array of days of the month names, starting 1 = January LongTimeFormat   Long version of the time to string format ShortDateFormat   Compact version of the date to string format ShortDayNames   An array of days of the week names, starting 1 = Sunday ShortMonthNames   An array of days of the month names, starting 1 = Jan ShortTimeFormat   Short version of the time to string format StrToDateTime   Converts a date+time string into a TDateTime value TimeAMString   Determines AM value in DateTimeToString procedure TimePMString   Determines PM value in DateTimeToString procedure TimeSeparator   The character used to separate display time fields TwoDigitYearCenturyWindow   Sets the century threshold for 2 digit year string conversions

Example code : Showing all of the date field formatting data types var   myDate : TDateTime; begin   // Set up our TDateTime variable with a full date and time :   // 5th of June 2000 at 01:02:03.004  (.004 milli-seconds)   myDate := EncodeDateTime(2000, 6, 5, 1, 2, 3, 4);   // Date only - numeric values with no leading zeroes (except year)   ShowMessage('              d/m/y = '+               FormatDateTime('d/m/y', myDate));   // Date only - numeric values with leading zeroes   ShowMessage('           dd/mm/yy = '+               FormatDateTime('dd/mm/yy', myDate));   // Use short names for the day, month, and add freeform text ('of')   ShowMessage('  ddd d of mmm yyyy = '+               FormatDateTime('ddd d of mmm yyyy', myDate));   // Use long names for the day and month   ShowMessage('dddd d of mmmm yyyy = '+               FormatDateTime('dddd d of mmmm yyyy', myDate));   // Use the ShortDateFormat settings only   ShowMessage('              ddddd = '+               FormatDateTime('ddddd', myDate));   // Use the LongDateFormat settings only   ShowMessage('             dddddd = '+               FormatDateTime('dddddd', myDate));   // Use the ShortDateFormat + LongTimeFormat settings   ShowMessage('                  c = '+               FormatDateTime('c', myDate)); end; Show full unit code                  d/m/y = 5/6/00              dd/mm/yy = 05/06/00     ddd d of mmm yyyy = Mon 5 of Jun 2000   dddd d of mmmm yyyy = Monday 5 of June 2000                 ddddd = 05/06/2000                dddddd = 05 June 2000                     c = 05/06/2000 01:02:03     Example code : Showing all of the time field formatting data types var   myDate : TDateTime; begin   // Set up our TDateTime variable with a full date and time :   // 5th of June 2000 at 01:02:03.004  (.004 milli-seconds)   myDate := EncodeDateTime(2000, 6, 5, 1, 2, 3, 4);   // Time only - numeric values with no leading zeroes   ShowMessage('     h:n:s.z = '+FormatDateTime('h:n:s.z', myDate));   // Time only - numeric values with leading zeroes   ShowMessage('hh:nn:ss.zzz = '+FormatDateTime('hh:nn:ss.zzz', myDate));   // Use the ShortTimeFormat settings only   ShowMessage('           t = '+FormatDateTime('t', myDate));   // Use the LongTimeFormat settings only   ShowMessage('          tt = '+FormatDateTime('tt', myDate));   // Use the ShortDateFormat + LongTimeFormat settings   ShowMessage('           c = '+FormatDateTime('c', myDate)); end; Show full unit code         h:m:s.z = 1:2:3.4   hh:mm:ss.zzz = 01:02:03.004              t = 01:02             tt = 01:02:03              c = 05/06/2000 01:02:03     Example code : Showing the effect of local date format settings var   myDate : TDateTime; begin   // Set up our TDateTime variable with a full date and time :   // 5th of June 2049 at 01:02:03.004  (.004 milli-seconds)   //   // Note that 49 is treated as 2049 as follows :   //               TwoDigitYearCenturyWindow => 50   //                            Current year => 2008 (at time of writing)   //      Subtract TwoDigitYearCenturyWindow => 1958   //            2 digit year to be converted => 49   //  Compare with the last 2 digits of 1958 => Less   //      So the year is in the next century => 2049   // (58 would be converted to 1958)   myDate := StrToDateTime('05/06/49 01:02:03.004');   // Demonstrate default locale settings   // Use the DateSeparator and TimeSeparator values   ShowMessage('dd/mm/yy hh:nn:ss = '+               FormatDateTime('dd/mm/yy hh:nn:ss', myDate));   // Use ShortMonthNames   ShowMessage('              mmm = '+FormatDateTime('mmm', myDate));   // Use LongMonthNames   ShowMessage('             mmmm = '+FormatDateTime('mmmm', myDate));   // Use ShortDayNames   ShowMessage('              ddd = '+FormatDateTime('ddd', myDate));   // Use LongDayNames   ShowMessage('             dddd = '+FormatDateTime('dddd', myDate));   // Use the ShortDateFormat string   ShowMessage('            ddddd = '+FormatDateTime('ddddd', myDate));   // Use the LongDateFormat string   ShowMessage('           dddddd = '+FormatDateTime('dddddd', myDate));   // Use the TimeAmString   ShowMessage('           hhampm = '+FormatDateTime('hhampm', myDate));   // Use the ShortTimeFormat string   ShowMessage('                t = '+FormatDateTime('t', myDate));   // Use the LongTimeFormat string   ShowMessage('               tt = '+FormatDateTime('tt', myDate));   // Use the TwoDigitCenturyWindow   ShowMessage('       dd/mm/yyyy = '+               FormatDateTime('dd/mm/yyyy', myDate));   ShowMessage('');   // Now change the defaults   DateSeparator      := '-';   TimeSeparator      := '_';   ShortDateFormat    := 'dd/mmm/yy';   LongDateFormat     := 'dddd dd of mmmm of yyyy';   TimeAMString       := 'morning';   TimePMString       := 'afternoon';   ShortTimeFormat    := 'hh:nn:ss';   LongTimeFormat     := 'hh : nn : ss . zzz';   ShortMonthNames[6] := 'JUN';   LongMonthNames[6]  := 'JUNE';   ShortDayNames[1]   := 'SUN';   LongDayNames[1]    := 'SUNDAY';   TwoDigitYearCenturyWindow := 75; // This means 49 is treated as 1949   // Set up our TDateTime variable with the same value as before   // except that we must use the new date and time separators   // The TwoDigitYearCenturyWindow variable only takes effect here   myDate := StrToDateTime('09-02-49 01_02_03.004');   // Use the DateSeparator and TimeSeparator values   ShowMessage('dd/mm/yy hh:nn:ss = '+               FormatDateTime('dd/mm/yy hh:nn:ss', myDate));   // Use ShortMonthNames   ShowMessage('              mmm = '+FormatDateTime('mmm', myDate));   // Use LongMonthNames   ShowMessage('             mmmm = '+FormatDateTime('mmmm', myDate));   // Use ShortDayNames   ShowMessage('              ddd = '+FormatDateTime('ddd', myDate));   // Use LongDayNames   ShowMessage('             dddd = '+FormatDateTime('dddd', myDate));   // Use the ShortDateFormat string   ShowMessage('            ddddd = '+FormatDateTime('ddddd', myDate));   // Use the LongDateFormat string   ShowMessage('           dddddd = '+FormatDateTime('dddddd', myDate));   // Use the TimeAmString   ShowMessage('           hhampm = '+FormatDateTime('hhampm', myDate));   // Use the ShortTimeFormat string   ShowMessage('                t = '+FormatDateTime('t', myDate));   // Use the LongTimeFormat string   ShowMessage('               tt = '+FormatDateTime('tt', myDate));   // Use the TwoDigitCenturyWindow   ShowMessage('       dd/mm/yyyy = '+               FormatDateTime('dd/mm/yyyy', myDate)); end; Show full unit code    dd/mm/yy hh:mm:ss = 05/06/49 01:02:03                 mmm = Jun                mmmm = June                 ddd = Sat                dddd = Saturday               ddddd = 05/06/2049              dddddd = 05 June 2049              hhampm = 01AM                   t = 01:02                  tt = 01:02:03          dd/mm/yyyy = 05/06/2049      dd/mm/yy hh:nn:ss = 05-06-49 01_02_03                 mmm = JUN                mmmm = JUNE                 ddd = SUN                dddd = SUNDAY               ddddd = 05-JUN-49              dddddd = SUNDAY 05 of JUNE of 1949              hhampm = 01morning                   t = 01_02_03                  tt = 01 _ 02 _ 03 . 004          dd/mm/yyyy = 05-06-1949

 

 

 

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;

 

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;

 

 

转自：http://www.delphibasics.co.uk/RTL.asp?Name=FormatDateTime

           http://bettereducation.com.au/it/yaf_postst448_Converts-a-date-or-time-or-datetime-string-into-a-TDateTime-value-in-Delphi.aspx