Zeller's Algorithm (Python)

#!/usr/bin/env python
from datetime import datetime

months = {"1":11, "2":12, "3":1, "4":2, "5":3, "6":4,
"7":5, "8":6, "9":7, "10":8, "11":9, "12":10}
days = {"1":"Monday", "2":"Tuesday","3":"Wednesday","4":"Thursday","5":"Friday","6":"Saturday","0":"Sunday"}
bMonth = "0"
bDay = "0"
bYear = "0"
bCent = "0"
today = datetime.now()
born = "You were born on a "


validInput = False
while (validInput == False):
    while(len(bYear)!=2):
        bYear = input("Want to know the day of the week you were born?\n Enter the two digit year: \n(e.g. if you were born in 1980 enter 80) YY ")
    try:
        tYear = int(bYear)
        if tYear >= 0 and tYear <= 99:
            validInput = True
            bYear = int(bYear)
    except ValueError:
      bYear = input("You made an invalid entry. \nEnter the two digit year: \n(e.g. if you were born in 1980 enter 80) YY ")

validInput = False
while (validInput == False):
    while(len(bCent)!=2):
        bCent = input("Enter the two digit century: \n(e.g. if you were born in 1980 enter 19) CC ")

    try:
        tCent = int(bCent)
        if tCent >= 0 and tCent <= 99:
            validInput = True
            bCent = int(bCent)
    except ValueError:
      bCent = input("You made an invalid entry. \nEnter the two digit century: \n(e.g. if you were born in 1980 enter 19) CC ")

validInput = False
while (validInput == False):
    while(len(bMonth)!=2):
        bMonth = input("Enter a number for the month: MM ")

    try:
        tMonth = int(bMonth)
        if tMonth >= 1 and tMonth <= 12:
            validInput = True
            bMonth = int(bMonth)
        else:
            bMonth = "0"
    except ValueError:
      bMonth = input("You made an invalid entry. \nEnter a number for the month: MM ")

validInput = False
while (validInput == False):
    while(len(bDay)!=2):
        bDay = input("Enter a number for the day: DD ")

    try:
        tDay = int(bDay)
        if bMonth == 1:
            if tDay >= 1 or tDay <=31:
                validInput = True
                bDay = int(bDay)
        elif bMonth == 2:
            if bYear%4 == 0:
                if tDay >=1 or tDay <= 29:
                    validInput = True
                    bDay = int(bDay)
            else:
                if tDay >=1 or tDay <= 28:
                    validInput = True
                    bDay = int(bDay)
        elif bMonth == 3:
            if tDay >= 1 or tDay <=31:
                validInput = True
                bDay = int(bDay)
        elif bMonth == 4:
            if tDay >= 1 or tDay <=30:
                validInput = True
                bDay = int(bDay)
        elif bMonth == 5:
            if tDay >= 1 or tDay <=31:
                validInput = True
                bDay = int(bDay)
        elif bMonth == 6:
            if tDay >= 1 or tDay <=30:
                validInput = True
                bDay = int(bDay)
        elif bMonth == 7:
            if tDay >= 1 or tDay <=31:
                validInput = True
                bDay = int(bDay)
        elif bMonth == 8:
            if tDay >= 1 or tDay <=31:
                validInput = True
                bDay = int(bDay)
        elif bMonth == 9:
            if tDay >= 1 or tDay <=30:
                validInput = True
                bDay = int(bDay)
        elif bMonth == 10:
            if tDay >= 1 or tDay <=31:
                validInput = True
                bDay = int(bDay)
        elif bMonth == 11:
            if tDay >= 1 or tDay <=30:
                validInput = True
                bDay = int(bDay)
        elif bMonth == 12:
            if tDay >= 1 or tDay <=31:
                validInput = True
                bDay = int(bDay)
        else:
            bDay = "0"
    except ValueError:
      bDay = input("You made an invalid entry. \nEnter a number for the day: DD ")

if today.year < int(str(bCent)+str(bYear)):
    born = "You will born on a "
A = int(months[str(bMonth)])
B = bDay
if A == 11 or A == 12:
    if bYear == 00:
        bYear = 99
        bCent = bCent - 1
    else:
        bYear = bYear - 1
C = bYear
D = bCent

W = int((13*A - 1) / 5)
X = int(C / 4)
Y = int(D / 4)
Z = int(W + X + Y + B + C - 2*D)
R = int((Z%7))

if (R < 0):
    R = (R+7)%6

print (born + days[str(R)])