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//This program will find the day from any date between 45BC to 9999AD.
//It uses the Julian Calendar between the dates 45BC and 1752AD.
//It assumes 45BC (the year the Julian calendar was introduced) is a leap year.
//The year does not exist, 3BC, 2BC, 1BC, 1AD....
//Type 'config' to change the date the Gregorian calendar takes effect.
#include <iostream>
#include <string>
using namespace std;
int main()
{
//Collect Data
int england=1752;
start:
cout << "\nDDDDD tt";
cout << "\nDD DD aa aa tt eee";
cout << "\nDD DD aa aaa tttt ee e";
cout << "\nDD DD aa aaa tt eeeee";
cout << "\nDDDDDD aaa aa tttt eeeee\n";
cout << "\n CCCCC lll lll tt";
cout << "\nCC C aa aa lll cccc uu uu lll aa aa tt oooo rr rr";
cout << "\nCC aa aaa lll cc uu uu lll aa aaa tttt oo oo rrr r";
cout << "\nCC C aa aaa lll cc uu uu lll aa aaa tt oo oo rr";
cout << "\n CCCCC aaa aa lll ccccc uuuu u lll aaa aa tttt oooo rr";
cout << "\n\nby Rik Potts";
string start;
cout << "\n\nEnter 'go' to begin or type 'config' for configuration: ";
cin >> start;
if (start!="go" && start!="config")
{
cout << start << " is not a valid entry. Please try again\n\n";
goto start;
}
if (start=="go") goto findday; else goto config;
//Configuration
config:
cout << "\nPlease enter the date you want the Gregorian (modern) calendar to take effect.";
cout << "\n\nDefault is 1752 which is when England began using the Gregorian";
cout << "\ncalendar. The Gregorian calendar was first introduced in 1582";
cout << "\nin Venice, France, Spain, Portugal and Netherlands. Germany in 1583";
cout << ",\nPrussia and Denmark in 1700, Sweden in 1753 and Russia in 1918!\n\n";
cout << "Please enter the date you want the Gregorian calendar to take effect: ";
cin >> england;
cout << "NOTE: You will have to set config each time you run the program.\n\n";
//Find the day (day)
findday:
cout << "The Gregorian (modern) calendar will take effect from " << england;
int day;
cout << "\nPlease enter the day (##): " ;
cin >> day;
if (day>31 || day<1)
{
cout << "\n" << day << " is not a valid day!\nPlease try again\n\n";
goto findday;
}
//Find the month (month)...
month:
string month;
cout << "Please enter the Month (abc): ";
cin >> month;
if (month!="feb" && month!="aug" && month!="mar" && month!="nov"
&& month!="jun" && month!="sep" && month!="dec" && month!="apr"
&& month!="jul" && month!="jan" && month!="oct" && month!="may")
{
cout << "\n" << month << " is not a valid month!\nPlease try again...\n\n";
goto month;
}
if (month=="feb" && day>29)
{
cout << "\nIt is not possible to have " << day << " days in February!";
cout << "\nPlease try again\n\n";
goto findday;
}
//Find the year (date)...
cent:
cout << "\nNOTE: If you need a BC date you DO ";
cout << "NOT need to use a minus sign (-)\n";
//Get the century (cent)
int cent;
cout << "Please enter the first two digits of the year (##__): ";
cin >> cent;
if (cent>99)
{
cout << "\n" << cent << " is not a valid entry.\nYou must enter a number below 99.\n";
goto cent;
}
//Get the year (year)
year:
int year;
cout << "Please enter the last two digits of the year (__##): ";
cin >> year;
if (year>99 || year<0)
{
cout << "\n" << year << " is not a valid entry.\nYou must enter a number below 99\n\n";
goto year;
}
//make the full year (date)
int date, numdate;
date=(100*cent) + year;
numdate=date;
if (date==0)
{
cout << "\nThe date 0000 is not valid because the Julian calendar uses 1BC";
cout << " instead\n\n";
goto cent;
}
//Is it a negative or positive year?...
norp:
string bc;
cout << "Is the year BC? (y/n) : ";
cin >> bc;
if (bc!="y" && bc!="n")
{
cout << bc << " is not a valid option. Please try again...";
goto norp;
}
if (bc=="y") date=-date;
if (date<=-46)
{
cout << "\nYou entered " << numdate << "BC. The Julian calendar was introduced ";
cout << "in 45BC.";
cout << "\nThis makes " << numdate << "BC invalid!\n";
goto cent;
}
int year2;
year2=year/4;
//Process and Validate Data
//Is the year a leap year?...
//Is the year on the gregorian or julian calendar?
int yl=1, nl=0;
if (date>=england) goto gregorian;
//Julian calendar
int jleap;
if (date>0 && (date%4==0)) jleap=yl; else jleap=nl;
if (date<0 && (date%4==-1)) jleap=yl; else jleap=nl;
goto validation;
//Gregorian calendar
gregorian:
int gleap;
gleap = ((date%4==0 && date%100!=0) || date % 400 == 0) ? yl : nl;
//Is the Month and Day combination correct?
validation:
if ((jleap==1 || gleap==1) && month=="feb" && day<=29) goto notfeb;
if ((jleap!=1 || gleap!=1) && month=="feb" && day==29)
{
cout << "\nThe 29th February is not a valid date because " << date;
cout << " \nisnt a leap year!\nPlease try again from the beginning\n\n";
goto findday;
}
if (month!="feb") goto notfeb;
if (!(day<=28 && day>=1))
{
cout << day << "\n is not a valid day!\nPlease try again\n\n";
goto findday;
}
notfeb:
if (month!="sep" && month!="apr" && month!="jun" && month!="nov") goto nsajn;
if (!(day<=30 && day>=1))
{
cout << day << "\n is not a valid day!\nPlease try again\n\n";
goto findday;
}
nsajn:
if (!(day<=31 && day>=1))
{
cout << day << "\n is not a valid day!\nPlease try again\n\n";
goto findday;
}
//Interpret Data
//Calculate the Monthcode
int monthcode;
if (month=="aug") monthcode=0;
if (month=="feb" || month=="mar" || month=="nov") monthcode=1;
if (month=="jun") monthcode=2;
if (month=="sep" || month=="dec") monthcode=3;
if (month=="apr" || month=="jul") monthcode=4;
if (month=="jan" || month=="oct") monthcode=5;
if (month=="may") monthcode=6;
//Which calendar to use?
if (date>=england) goto gregoriansum;
//Is the leap year compensation required?
int ujleap, ugleap;
ujleap=jleap;
ugleap=gleap;
if (month!="jan" && month!="feb") ujleap=nl;
if (month!="jan" && month!="feb") ugleap=nl;
//Julian Formula...
//(Day + MonthCode + Year + Year/4 + 5 – Century – isLeapJanFeb?) % 7
int jresult;
if (date<0) jresult=(day + monthcode - year - (year2) + 5 - cent )%(-7);
else
jresult=(day + monthcode + year + (year2) + 5 - cent - ujleap)%7;
goto weekday;
//Gregorian Formula...
gregoriansum:
//(Day + MonthCode + Year + Year/4 – 2×(Century%4) – isLeapJanFeb?) % 7
int gresult;
gresult=(day + monthcode + year + (year2) - (2*(cent%4)) - ugleap)%7;
//Assign day code to word.
weekday:
int weekday;
string result;
weekday = (date<england) ? jresult : gresult;
if (weekday==0) result="Monday";
if (weekday==1 || weekday==-6) result="Tuesday";
if (weekday==2 || weekday==-5) result="Wednesday";
if (weekday==3 || weekday==-4) result="Thursday";
if (weekday==4 || weekday==-3) result="Friday";
if (weekday==5 || weekday==-2) result="Saturday";
if (weekday==6 || weekday==-1) result="Sunday";
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