Dates and Times

Format characters

The complete list of formatting characters can be found in formatchars doc.

How can I get current date and time?

1. Add sysutils to the uses section.
2. Use Now to get current date time.

From here you have choices.

• You can use DateToStr to get only the date string from Now.
• You can use TimeToStr to get only the time string from Now.
• You can use DateTimeToStr to get the date time string from Now.
• You can use FormatDateTime to customise the date time string from Now.

Here is an example.

program DateTimeCurrent;

uses
  SysUtils;

begin

  // Display current date only with the default formatting
  WriteLn('Date: ', DateToStr(Now));

  // Display current time only with the default formatting
  Writeln('Time: ', TimeToStr(Now));

  // Display current timestamp with the default formatting
  Writeln('Now is (default format): ', DateTimeToStr(Now));

  // Display timestamp with custom formatting
  Writeln('Now is (custom format) : ',
          FormatDateTime('yyyy-mm-dd hh:nn:ss.z', Now));
  Writeln('Now is (custom format) : ',
          FormatDateTime('dd-mmm-yy hh:nn AM/PM', Now));

  // Display timestamp in long format -- Tuesday, 9 January 2024 12:08:17 PM
  Writeln('Now is (custom format) : ', FormatDateTime('dddddd tt', Now));

  // Pause console
  ReadLn;
end.

How to get Unix epoch time?

1. In uses section add SysUtils and DateUtils.
2. Call DateTimeToUnix(Now);.

program DateTimeUnix;

uses
  SysUtils,
  DateUtils;

var
  unixTime: integer;

begin
  unixTime := DateTimeToUnix(Now);
  Writeln('Current time in Unix epoch time is: ', unixTime);

  // Pause console;
  ReadLn;
end.

Finding days or time between dates

You can use any of the following to find days or time between dates.

• YearsBetween - The number of whole years between two TDateTime values
• MonthsBetween - The number of whole months between two TDateTime values
• WeeksBetween - The number of whole weeks between two TDateTime values
• DaysBetween - Number of whole days between two TDateTime values.
• HoursBetween - The number of whole hours between two TDateTime values.
• MinutesBetween - The number of whole minutes between two TDateTime values.
• SecondsBetween - The number of whole seconds between two TDateTime values.
• MilliSecondsBetween - The number of whole milliseconds between two TDateTime values.

Here is an example of using SecondsBetween and DaysBetween.

program DateTimeBetween;

uses
  SysUtils,
  DateUtils;

var
  diffSec, diffDay: integer;

begin

  // Seconds between 2 times
  diffSec := SecondsBetween(StrToTime('18:30'), StrToTime('07:35'));
  WriteLn('The seconds between 18:30 and 07:35 is: ', diffSec, ' seconds');

  // Days between 2 dates
  diffDay := DaysBetween(StrToDate('09/01/2024'), StrToDate('01/01/2015'));
  WriteLn('The days difference between 2024-01-05 and 2015-01-01 is: ', diffDay, ' days');

  // Seconds between 2 dates
  // Casting diffsec to float for nicer formatting
  diffSec := SecondsBetween(StrToDate('09/01/2024'), StrToDate('01/01/2015'));
  WriteLn('The seconds between 2024-01-05 and 2015-01-01 is: ', Format('%n', [diffSec + 0.0]),' seconds');

  ReadLn;
end.

Simple profiling a section of a program

1. Place the GetTickCount64 before and after a specific section of code.
2. Calculate the elapsed time in milliseconds by subtracting the initial value from the final value obtained from GetTickCount64.

Warning

GetTickCount64 returns an increasing clock tick count in milliseconds. It is useful for time measurements, but no assumptions should be made as to the interval between the ticks.

https://www.freepascal.org/daily/doc/rtl/sysutils/gettickcount64.html

Here is an example.

program DateTimeBenchmark;

uses
  SysUtils;

var
  startTime, endTime: QWord;

begin

  // Get start time.
  startTime := GetTickCount64;

  // Simulate a long running task
  Sleep(1000);

  // Get end time
  endTime := GetTickCount64;

  // Display time elapsed
  Writeln('Time elapsed: ', (endTime-startTime), ' ms');

  // Pause console
  ReadLn;
end.

How can I compare two dates?

Use the comparison operators (<, >, <=, >=, =) to compare two TDateTime values.

Consider the following example.

program DateTimeComparison;

uses
  SysUtils,
  DateUtils;

var
  surveyReleaseDate: TDateTime;

begin

  // Set survey release date
  surveyReleaseDate := StrToDate('15/12/2024');

  if surveyReleaseDate < Now then
  begin
    WriteLn('You can release survey results now');
    WriteLn('You''re behind by ', DaysBetween(Now, surveyReleaseDate), ' days.');
  end
  else
  begin
    WriteLn('You CANNOT release survey results! Wait!');
    WriteLn('You can release results in ', DaysBetween(Now, surveyReleaseDate), ' days.');
  end;

  // Pause console
  ReadLn;
end.

How do I parse a string date in dd-mmm-yy format?

Use ScanDateTime from DateUtils.

Take a look at this example.

program ParseDate;

uses
  SysUtils,
  DateUtils;

var
  dateString: string;
  parsedDate: TDateTime;

begin

  // date to parse
  dateString := '03-MAR-24';

  // default value of parsed date. If conversion fails, use this value
  parsedDate := Default(TDateTime);

  try
    parsedDate := ScanDateTime('dd?mmm?yy', dateString);
    // Now dateValue contains the parsed date, else ScanDateTime will raise an exception

    // Use FormatDateTime to format the parsed date as needed
    WriteLn('Parsed date                : ', DateToStr(parsedDate));
    WriteLn('Parsed date (custom format): ', FormatDateTime('dddddd tt', parsedDate));
    WriteLn('Parsed date (custom format): ', FormatDateTime('yyyy-mm-dd hh:nn:ss', parsedDate));
  except
    on E: EConvertError do
      WriteLn('Invalid date string');
  end;

  // Pause console
  Readln;
end.