#julian.py
#calculate julian date of any year/month/day input

#a program with lots of if statements and no loops

year = int(input("Enter year: "))
month = int(input("Enter month number: "))
day = int(input("Enter day: "))

if month<1 or month>12:
    print( "bogus month.  Bye!")
    quit()
  
elif day<1 or day>31:
    print( "bogus day.  Bye!")
    quit()
  
elif year < 1753:
    print( "Sorry, calendar was wacky before 1753.  Bye!")
    quit()
  

  #test for leapyear.  
  #a year is a leap year if evenly divisible by 4 but not also evenly
  #divisible by 100 unless also evenly divisible by 400.
  #I.e. century years are not normally leap years unless they are also 400
  #years.  1800, 1900, 2100 are not leap years, but 2000 is.
if year%4==0 and year%100!=0 or year%400==0:
    is_leap = True
else:
    is_leap = False

  #test that month day combo is valid.  have already checked that day is <= 31
  #So know that 31 day months are valid.
if month==4 or month==6 or month==9 or month==11:  #30 day months
    if day > 30:   #i.e. is 31
        if month == 4:
            print( "April has only 30 days.  Bye!")
        elif month == 6:
            print( "June has only 30 days.  Bye!")
        elif month == 9:
            print( "September has only 30 days.  Bye!")
        elif month == 11:
            print( "November has only 30 days.  Bye!")
        quit()
elif month == 2:   #Feb.    
    if not is_leap and day > 28:   #not a leap year
        print( "February has only 28 days this year.  Bye!")
        quit()
    elif is_leap and day > 29:    #is leap year
        print( "February has only 29 days this year.  Bye!")
        quit()

  #determine the number of days in all the previous months
previousMonthDays = 0
if month > 1:
    previousMonthDays += 31   #Jan
if month > 2:
    previousMonthDays += 28   #Feb
    if is_leap:
      previousMonthDays += 1    #Feb 29
  
if month > 3:              
    previousMonthDays += 31   #Mar 
if month > 4:
    previousMonthDays += 30   #Apr
if month > 5:
    previousMonthDays += 31   #May
if month > 6:
    previousMonthDays += 30   #Jun
if month > 7:
    previousMonthDays += 31   #Jul
if month > 8:
    previousMonthDays += 31   #Aug
if month > 9:
    previousMonthDays += 30   #Sep
if month > 10:
    previousMonthDays += 31   #Oct
if month > 11:
    previousMonthDays += 30   #Nov

julian = previousMonthDays + day  #plus this month's day
 
print( "Julian date: ", julian)