Program Jules;
{
  All of the explanation needed is the source.

  "May this routine make all your code run faster"
                            - Programmer's Prayer
}


Type
  Str3 = string[3];  {for a month name}
  str9 = string[9];
Var
  Date1,Date2    : string[12]; {the dates to compare}
  Number_of_days : integer;    {Number of days between the two dates}

Function Number_of_Month (Month : str3) : integer;
{Returns the sequential number of the month; Jan=1 & Dec = 12}
Var
  Temp : integer;
  Dates : string[36];
Begin
  {Notice how I scan the string. Less code than a case!}
  Dates := 'JanFebMarAprMayJunJulAugSepOctNovDec';
  Number_of_Month := round((pos(Month,Dates)-1)/3) +1;
End;

function Since_Beginning (month,day,year : integer) : integer;
var
   DayCount  : integer;   {Holds the number of days}
   Temp      : integer;   {Just a temporary holding integer}
   Num_Leaps : integer;   {Holds the number of leap years}
Begin
  Num_Leaps := 0;
  DayCount  := 0;
  Writeln;
  Writeln('Scanning ',month,'/',day,'/',year,' ...');
  for Temp := 1 to year do   {Gets the number of leap years}
    If (temp mod 4) = 0 then Num_Leaps := Num_Leaps + 1;
  Writeln('Found ',num_leaps,' leap years occuring');
  DayCount := (year * 365) + Num_Leaps;  {calcs year & leap year}
  Writeln('Making ',abs(daycount),' days in ',year,' YEARS');
  DayCount := DayCount + Day; {adds in days}
  Writeln('Plus ',day,' days makes ',abs(daycount),
          ' days in YEAR + DAY');

  For Temp := 1 to Month-1 do
{
 Couldn't help but put a large case here.
 The number is the number of days in that month. Feb is 28 because
 the leap year counter takes the leap year into effect
}
  Begin
    Case Temp of
      1 : DayCount := DayCount + 31; {jan}
      2 : DayCount := DayCount + 28; {feb}
      3 : DayCount := DayCount + 31; {mar}
      4 : DayCount := DayCount + 30; {apr}
      5 : DayCount := DayCount + 31; {may}
      6 : DayCount := DayCount + 30; {jun}
      7 : DayCount := DayCount + 31; {jul}
      8 : DayCount := DayCount + 31; {aug}
      9 : DayCount := DayCount + 30; {sep}
     10 : DayCount := DayCount + 31; {oct}
     11 : DayCount := DayCount + 30; {nov}
     12 : DayCount := DayCount + 31; {dec}
    end; {case of temp}
  end; {for loop}
  Since_Beginning := DayCount;
  Writeln('Plus ',month,' months makes ',abs(daycount),
          ' days since 00/00/00');
end; {function SINCE_BEGINNING}


Function Days_Elapsed (date1,date2 : str9) : integer;
Var
  Month1,Day1,Year1,
  Month2,Day2,Year2 : integer; {sets of dates}
  Temp1,Temp2       : integer; {for the VAL function}
Begin
  Month1 := Number_of_Month(Copy(date1,4,3));  {gets the month number}
  Month2 := Number_of_Month(Copy(date2,4,3));  {gets the month number}
  Val(copy(date1,1,2),Day1,Temp2);      {get everything into numerics}
  Val(copy(date2,1,2),Day2,Temp2);      { "        "      "      "   }
  Val(copy(date1,8,2),year1,temp2);     { "        "      "      "   }
  Val(copy(date2,8,2),year2,temp2);     { "        "      "      "   }
  Val(copy(date1,8,2),year1,temp2);     { "        "      "      "   }
  Val(copy(date2,8,2),year2,temp2);     { "        "      "      "   }
  Days_Elapsed := Since_Beginning(month2,day2,year2) -
                  Since_Beginning(month1,day1,year1);
                  {The difference of the two numbers}
end;

Begin {Main}
  Date1 := '27 Jan 64';  {My birthday}
  Date2 := '20 Nov 85';  {When I last edited this program}
  ClrScr;                {If you want originality, call an author...}
  Writeln('JULES   -  Finds the number of days between two dates ',
          'using a JULIAN manner.');
  Writeln('Author  -  David Strickler');
  Writeln('Address -  FIDO 101/45  [Midnight DEC]');
  Writeln;
  Writeln('This program shows a pretty good way to find the number');
  Writeln('of days between two dates. It is reasonably fast and');
  Writeln('has a mininum of source code to it. Please use it as');
  Writeln('you wish. The only right I claim, is that is it officialy');
  Writeln('in the Public Domain.');
  Writeln;
  {Call the main function. Very neat & clean. Two in, one out}
  Number_of_Days := Days_Elapsed(date1,date2);
  Writeln('Number of days between ',date1,' and ',date2,' is ',
           Number_of_days);
End.