Pascal - Date & Time
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- Category: Chapter 4
- Published: Monday, 15 April 2013 14:01
- Written by Sternas Stefanos
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Most of the software you write needs implementing some form of date functions returning current date and time. Dates are so much part of everyday life that it becomes easy to work with them without thinking. Pascal also provides powerful tools for date arithmetic that makes manipulating dates easy. However, the actual name and workings of these functions are different for different compilers.
1. Getting the Current Date & Time:
Pascal's TimeToString function gives you the current time in a colon(: ) delimited form. The following example shows how to get the current time:
program TimeDemo; uses sysutils; begin writeln ('Current time : ',TimeToStr(Time)); end.
When the above code was compiled and executed, it produced following result:
Current time : 18:33:08
The Date function returns the current date in TDateTime format. The TDateTime is a double value, which needs some decoding and formatting. The following program demonstrates how to use it in your program to display the current date:
Program DateDemo; uses sysutils; var YY,MM,DD :Word;begin writeln ('Date : ',Date); DeCodeDate(Date,YY,MM,DD); writeln (format ('Today is (DD/MM/YY): %d/%d/%d ',[dd,mm,yy])); readln; // to see the output end.
When the above code was compiled and executed, it produced following result:
Date: 4.195700000000000E+004 Today is (DD/MM/YY):14/11/2014
The Now function returns the current date and time:
Program DatenTimeDemo; uses sysutils; begin writeln ('Date and Time at the time of writing : ',DateTimeToStr(Now)); end.
When the above code was compiled and executed, it produced following result:
Date and Time at the time of writing : 23/7/2012 18:51:
Free Pascal provides a simple time stamp structure named TTimeStamp, which has the following format:
type TTimeStamp= record Time:Integer; Date:Integer; end;
2. Various Date & Time Functions:
Free Pascal provides the following date and time functions:
| S.N | Function Name & Description |
|---|---|
| 1 | function DateTimeToFileDate(DateTime: TDateTime):LongInt; Convert DateTime type to file date. |
| 2 | function DateTimeToStr( DateTime: TDateTime):; Construct string representation of DateTime |
| 3 | function DateTimeToStr(DateTime: TDateTime; const FormatSettings: TFormatSettings):; Construct string representation of DateTime |
| 4 | procedure DateTimeToString(out Result: ;const FormatStr: ;const DateTime: TDateTime); Construct string representation of DateTime |
| 5 | procedure DateTimeToString( out Result: ; const FormatStr: ; const DateTime: TDateTime; const FormatSettings: TFormatSettings ); Construct string representation of DateTime |
| 6 | procedure DateTimeToSystemTime( DateTime: TDateTime; out SystemTime: TSystemTime ); Convert DateTime to system time |
| 7 | function DateTimeToTimeStamp( DateTime: TDateTime):TTimeStamp;Convert DateTime to timestamp |
| 8 | function DateToStr( Date: TDateTime ):; Construct string representation of date |
| 9 | function DateToStr( Date: TDateTime; const FormatSettings: TFormatSettings ):; Construct string representation of date |
| 10 | function Date: TDateTime; Get current date |
| 11 | function DayOfWeek( DateTime: TDateTime ):Integer; Get day of week |
| 12 | procedure DecodeDate( Date: TDateTime; out Year: Word; out Month: Word; out Day: Word ); Decode DateTime to year month and day |
| 13 | procedure DecodeTime( Time: TDateTime; out Hour: Word; out Minute: Word; out Second: Word; out MilliSecond: Word ); Decode DateTime to hours, minutes and seconds |
| 14 | function EncodeDate( Year: Word; Month: Word; Day: Word ):TDateTime; Encode year, day and month to DateTime |
| 15 | function EncodeTime( Hour: Word; Minute: Word; Second: Word; MilliSecond: Word ):TDateTime; Encode hours, minutes and seconds to DateTime |
| 16 | function FormatDateTime( const FormatStr: ; DateTime: TDateTime ):; Return string representation of DateTime |
| 17 | function FormatDateTime( const FormatStr: ; DateTime: TDateTime; const FormatSettings: TFormatSettings ):; Return string representation of DateTime |
| 18 | function IncMonth( const DateTime: TDateTime; NumberOfMonths: Integer = 1 ):TDateTime; Add 1 to month |
| 19 | function IsLeapYear( Year: Word ):Boolean; Determine if year is leap year |
| 20 | function MSecsToTimeStamp( MSecs: Comp ):TTimeStamp; Convert number of milliseconds to timestamp |
| 21 | function Now: TDateTime; Get current date and time |
| 22 | function StrToDateTime( const S: ):TDateTime; Convert string to DateTime |
| 23 | function StrToDateTime( const s: ShortString; const FormatSettings: TFormatSettings ):TDateTime; Convert string to DateTime |
| 24 | function StrToDateTime( const s: AnsiString; const FormatSettings: TFormatSettings ):TDateTime; Convert string to DateTime |
| 25 | function StrToDate( const S: ShortString ):TDateTime; Convert string to date |
| 26 | function StrToDate( const S: Ansistring ):TDateTime; Convert string to date |
| 27 | function StrToDate( const S: ShortString; separator: Char ):TDateTime; Convert string to date |
| 28 | function StrToDate( const S: AnsiString; separator: Char ):TDateTime; Convert string to date |
| 29 | function StrToDate( const S: ShortString; const useformat: ; separator: Char ):TDateTime; Convert string to date |
| 30 | function StrToDate( const S: AnsiString; const useformat: ; separator: Char ):TDateTime; Convert string to date |
| 31 | function StrToDate( const S: PChar; Len: Integer; const useformat: ; separator: Char = #0 ):TDateTime; Convert string to date |
| 32 | function StrToTime( const S: Shortstring ):TDateTime; Convert string to time |
| 33 | function StrToTime( const S: Ansistring ):TDateTime; Convert string to time |
| 34 | function StrToTime( const S: ShortString; separator: Char ):TDateTime; Convert string to time |
| 35 | function StrToTime( const S: AnsiString; separator: Char ):TDateTime; Convert string to time |
| 36 | function StrToTime( const S: ; FormatSettings: TFormatSettings ):TDateTime; Convert string to time |
| 37 | function StrToTime( const S: PChar; Len: Integer; separator: Char = #0 ):TDateTime; Convert string to time |
| 38 | function SystemTimeToDateTime( const SystemTime: TSystemTime ):TDateTime; Convert system time to datetime |
| 39 | function TimeStampToDateTime( const TimeStamp: TTimeStamp ):TDateTime; Convert time stamp to DateTime |
| 40 | function TimeStampToMSecs( const TimeStamp: TTimeStamp ):comp; Convert Timestamp to number of milliseconds |
| 41 | function TimeToStr( Time: TDateTime ):; Return string representation of Time |
| 42 | function TimeToStr( Time: TDateTime; const FormatSettings: TFormatSettings ):; Return string representation of Time |
| 43 | function Time: TDateTime; Get current time |
The following example illustrates the use of some of the above functions:
ProgramDatenTimeDemo; uses sysutils;var year, month, day, hr, min, sec, ms:Word;begin writeln ('Date and Time at the time of writing : ',DateTimeToStr(Now)); writeln('Today is ',LongDayNames[DayOfWeek(Date)]); writeln; writeln('Details of Date: '); DecodeDate(Date,year,month,day); writeln (Format('Day: %d',[day])); writeln (Format('Month: %d',[month])); writeln (Format('Year: %d',[year])); writeln; writeln('Details of Time: '); DecodeTime(Time,hr, min, sec, ms); writeln (format('Hour: %d:',[hr])); writeln (format('Minutes: %d:',[min])); writeln (format('Seconds: %d:',[sec])); writeln (format('Milliseconds: %d:',[hr]));end.
When the above code was compiled and executed, it produced following result:
Date and Time at the time of writing : 7/24/2012 8:26: Today is Tuesday Details of Date: Day:24 Month:7 Year: 2012 Details of Time: Hour: 8 Minutes: 26 Seconds: 21 Milliseconds: 8