Check Which Day Of The Year in Python

# The program checks what day it was or is of the year
# The program is written on mathematical calculation
# Script wrote by Ayan, contact : ayanu881@gmail.com


#month representing values

def main():
    months={
        "jan":1,
        "feb":4,
        "mar":4,
        "apr":0,
        "may":2,
        "jun":5,
        "jul":0,
        "aug":3,
        "sep":6,
        "oct":1,
        "nov":4,
        "dec":6
    }
    days_in_week=["Saturday","Sunday","Monday","Tuesday","Wednesday","Thursday","Friday"]

    CURRENT_YEAR=2021

    while True:
        year=int(input("year input:"))
        wmonth=input("First three letters of month:")
        day=int(input("Enter day:"))

        if len(wmonth)>3 or day>31:
            print("Wrong Input, try again")
            continue

        #get last numbers of the year, I call it year extension
        year_ext=year-1900

        #check if the year is leap year so we can perform later calculation
        def isleap_year():
            if year_ext%4==0:
                return True
            return False

        #default value
        leap_day_cal=0

        if isleap_year():
            if wmonth=="feb" or wmonth=="jan":
                leap_day_cal=(year_ext/4)-1
            else:
                leap_day_cal=year_ext/4

        else:
            leap_day_cal=year_ext/4



        total_cal=leap_day_cal+year_ext+day+months[wmonth]

        which_day_of_weak=days_in_week[int(total_cal%7)]

        if year<CURRENT_YEAR:
            print(f"It was {which_day_of_weak}")
        elif year==CURRENT_YEAR:
            print(f"It is {which_day_of_weak}")
        else:
            print(f"It is {which_day_of_weak}")


        option=input("Do you want to give nother try:(y/n)")

        if option.lower()=='y' or option in ['y']:
            main()
        else:
            exit()


if __name__=="__main__":
    main()