Friday 13th Lister DMcG

#'Friday 13ths since 1700' Lister
#for Python 2.x
#by Dominic D. McGough
#Friday, 23rd June, 2017

def weekDay(year, month, day):
    offset = [0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334]
    week   = ['Sunday',
              'Monday',
              'Tuesday',
              'Wednesday',
              'Thursday',
              'Friday',
              'Saturday']
    afterFeb = 1
    if month > 2: afterFeb = 0
    aux = year - 1700 - afterFeb
    # dayOfWeek for 1700/1/1 = 5, Friday
    dayOfWeek  = 5
    # partial sum of days between current date and 1700/1/1
    dayOfWeek += (aux + afterFeb) * 365
    # leap year correction
    dayOfWeek += aux / 4 - aux / 100 + (aux + 100) / 400
    # sum monthly and day offsets
    dayOfWeek += offset[month - 1] + (day - 1)
    dayOfWeek %= 7
    return week[dayOfWeek]

import datetime
now = datetime.datetime.now()
thisYear = now.year
count = 0

for year in range(1700, 2017+1):
    for month in range(1, 12+1):
        if weekDay(year, month, 13) == "Friday":
            print (str(13) + "/" + str(month) + "/" + str(year))
            count +=1

print("There's been " + str(count) + " Friday 13ths since 1700!")