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標題: [Delphi] 時間處理 [打印本頁]

作者: admin    時間: 2012-4-7 23:21     標題: [Delphi] 時間處理

uses SysUtils and DateUtils

(一)
var
   date1, date2, date3 : TDateTime;
begin
   date1 := Yesterday;      
   date2 := Date;           
   date3 := Tomorrow;   
   date4 := Now;            
end;

date1 會是 12/02/2012 00:00:00
date2 會是 13/02/2012 00:00:00
date3 會是 14/02/2012 00:00:00
date4 會是 13/02/2012 08:15:45


(二) 長短月份(month)名稱

var
   month : Integer;
begin
   for month := 1 to 12 do
   begin
     ShowMessage(ShortMonthNames[month]);
     ShowMessage(LongMonthNames[month]);
   end;
end;

結果顯示

Jan
January
Feb
February
Mar
March
Apr
April
May
May
Jun
June
Jul
July
Aug
August
Sep
September
Oct
October
Nov
November
Dec
December

(三) 長短周日(day)名稱

var
   day : Integer;
begin
   for day := 1 to 7 do
   begin
     ShowMessage(ShortDayNames[day]);
     ShowMessage(LongDayNames[day]);
   end;
end;


結果顯示

Sun
Sunday
Mon
Monday
Tue
Tuesday
Wed
Wednesday
Thu
Thursday
Fri
Friday
Sat
Saturday


(四) 日期計算


DayOfTheMonth  Gives the day of month index for a TDateTime value
DaysBetween    Gives the whole number of days between 2 dates
DaysInAMonth   Gives the number of days in a month
DaysInAYear    Gives the number of days in a year
DayOfTheYear  Gives the number of days from Jan 1 of the year
    eg:   exactdays := IntToStr(DayOfTheYear(MonthCalendar1.Date));
DecodeDate     Extracts the year, month, day values from a TDateTime var.
EncodeDate     Build a TDateTime value from year, month and day values


IncMillisecond
Increments a TDateTime variable by + or - number of milliseconds
IncSecond
Increments a TDateTime variable by + or - number of seconds
IncMinute
Increments a TDateTime variable by + or - number of minutes
IncDay         Increments a TDateTime variable by + or - number of days
     eg:     Convert threee digits of dayoftheYear back to DataTime Format
    date1: TDateTime;
    days1 : integer;
    date1 := IncDay( EncodeDate(2000+year1,1,1), days1-1);
    MonthCalendar.Date := date1;

IncMonth
Increments a TDateTime variable by a number of months
IncYear
Increments a TDateTime variable by a number of years


IsLeapYear     Returns true if a given calendar year is a leap year

MinsPerDay     Gives the number of minutes in a day


例子


  Mydate, Mytime: TDateTime;
  strDate, strTime: String;


  Mydate:= EncodeDate(2012,4,5); //year, month, day
  strDate := dateToStr(Mydate);
  Mytime:= EncodeTime(15,33,35,3); //hour, min, sec, msec
  strTime := TimeToStr(Mytime);

  還有 dateTimeToStr


(五) 顯示date 及 time 值的不同格式


var
   myDate : TDateTime;

begin
   // Set up our TDateTime variable with a full date and time :
   // 09/02/2000 at 05:06:07.008 (.008 milli-seconds)
   myDate := EncodeDateTime(2000, 2, 9, 5, 6, 7, 8);

   // 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));

   ShowMessage('');

   // 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;

The ShowMessage routine shows the following outputs :

               d/m/y = 9/2/00
            dd/mm/yy = 09/02/00
   ddd d of mmm yyyy = Wed 9 of Feb 2000
dddd d of mmmm yyyy = Wednesday 9 of February 2000
               ddddd = 09/02/2000
              dddddd = 09 February 2000
                   c = 09/02/2000 01:02:03

             h:n:s.z = 1:2:3.4
        hh:nn:ss.zzz = 01:02:03.004
                   t = 01:02
                  tt = 01:02:03
                   c = 09/02/2000 01:02:03

The above output uses default values of a number of formatting control variables. These are covered

in the next section:


Formatting control variables
The variables and their default values are given below. Note that these control conversions of date

time values to strings, and sometimes from strings to date time values (such as DateSeparator).


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





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