檢查日期時間合不合法

procedure CheckDate(var nYear: Integer; var nMonth: Integer;
    var nDay: Integer);
begin
  //Check day
  case nMonth of
  1, 3, 5, 7, 8, 10, 12: begin
    //31 days
    if(nDay >=31) then
    begin
      //進位
      nMonth:=nMonth+1;
      nDay:=nDay-31;
      if(nMonth = 2) then
      begin
        if(nDay >= 28) then
          //還要進位
          CheckDate(nYear, nMonth, nDay);
      end
      else if(nDay >= 30) then
        //還要進位
        CheckDate(nYear, nMonth, nDay);
    end
    else if(nDay < 0) then
    begin
      //退位
      nMonth:=nMonth-1;
      //if(nMonth
    end;
    end;//break
  4, 6, 9, 11: begin
    //30 days
    end;//break
  2: begin
    if(((nYear-1900) mod 4) = 0) then
    begin
      //29 days
    end
    else
    begin
      //29 days
    end;
    end;//break
  end;
  //Check month
  if(nMonth > 12) then
  begin
    Inc(nYear);
    Dec(nMonth, 12);
  end
  else if(nMonth < 0) then
  begin
    Dec(nYear);
    nMonth:=12+nMonth;
  end;
end;
//---------------------------------------------------------------------------

procedure CheckDateTime(var nYear: Integer; var nMonth: Integer;
    var nDay: Integer; var nHour: Integer; var nMin: Integer;
    var nSec: Integer; var nMSec: Integer);
var
  a: Integer;

begin
  //Check Millisecond.
  if(nMSec >= 1000) then
  begin
    //進位
    a:=nMSec div 1000;
    nSec:=nSec+a;
    nMSec:=nMSec-a*1000;
  end
  else if(nMSec < 0) then
  begin
    //退位
    a:=nMSec div 1000;
    Inc(a);
    nSec:=nSec-a;
    nMSec:=a*1000+nMSec;
  end;
  //Check second.
  if(nSec >= 60) then
  begin
    //進位
    a:=nSec div 60;
    nMin:=nMin+a;
    nSec:=nSec-a*60;
  end
  else if(nSec < 0) then
  begin
    //退位
    a:=nSec div 60;
    Inc(a);
    nMin:=nMin-a;
    nSec:=a*60+nSec;
  end;
  //Check minute.
  if(nMin >= 60) then
  begin
    //進位
    a:=nMin div 60;
    nHour:=nHour+a;
    nMin:=nMin-a*60;
  end
  else if(nMin < 0) then
  begin
    //退位
    a:=nMin div 60;
    Inc(a);
    nHour:=nHour-a;
    nMin:=a*60+nMin;
  end;
  CheckDate(nYear, nMonth, nDay);
end;
//---------------------------------------------------------------------------