day_occurrence_calculator

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Filename: day_occurrence_calculator.py
# Version: 1.0.0
# Author: Jeoi Reqi

"""
Description:
    - This script calculates the occurrences of a specified day falling on each day of the week within a given time period.

Requirements:
    - Python 3.x

Functions:
    - main():
        - Prompts the user to enter start and end years, start and end months, and a day of the month.
        - Calculates the occurrences of the specified day falling on each day of the week within the specified period.
        - Prints the results in a formatted table.

    - get_day_of_week(year, month, day):
        - Returns the index of the day of the week for a given date.
        - 0 for Monday, 1 for Tuesday, ..., 6 for Sunday.
        - Uses Zeller's Congruence algorithm:

            h = (q + ⌊5 * 13 * (m + 1) / 5⌋ + K + ⌊K / 4⌋ + ⌊J / 4⌋ - 2 * J) mod 7

Usage:
    - Run the script and follow the prompts to enter start and end years, start and end months, and a day of the month.
    - The script will then calculate and display the occurrences of the specified day falling on each day of the week.

Additional Notes:
    - Ensure the input values are within valid ranges:
    - Years should be positive integers, months should be between 1 and 12,
    - Days of the month should be between 1 and 31.
"""

def main():
    """
    Prompts the user to enter start and end years, start and end months, and a day of the month.
    Calculates the occurrences of the specified day falling on each day of the week within the specified period.
    Prints the results in a formatted table.
    """
    start_year = int(input("Enter the start year: "))
    start_month = int(input("Enter the start month (1-12): "))
    end_year = int(input("Enter the end year: "))
    end_month = int(input("Enter the end month (1-12): "))
    day_of_month = int(input("Enter the day of the month you want to count occurrences for (1-31): "))

    if (start_year < 0 or end_year < start_year or
            start_month < 1 or start_month > 12 or
            end_month < 1 or end_month > 12 or
            day_of_month < 1 or day_of_month > 31):
        print("Invalid input. Please enter valid years, valid months, and a valid day of the month.")
        return

    day_names = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"]
    counts = [0] * 7

    for year in range(start_year, end_year + 1):
        start = start_month if year == start_year else 1
        end = end_month + 1 if year == end_year else 13
        for month in range(start, end):
            # Check if the specified day of the month falls on the same day of the week
            day_of_week = get_day_of_week(year, month, day_of_month)
            counts[day_of_week] += 1

    print()
    print("-" * 88)
    print("{:^88}".format("Occurrences of the specified day ({}) falling on each day of the week (Monday to Sunday)".format(day_of_month)))
    print("-" * 88)
    print("{:^44}{:^44}".format("Day", "Count"))
    print("-" * 88)
    for i in range(7):
        print("{:^44}{:^44}".format(day_names[i], counts[i]))
    print("-" * 88)
    print()

    return 0

def get_day_of_week(year, month, day):
    """
    Returns the index of the day of the week for a given date.
    0 for Monday, 1 for Tuesday, ..., 6 for Sunday.
    Uses Zeller's Congruence algorithm.
    """
    if month < 3:
        month += 12
        year -= 1
    K = year % 100
    J = year // 100
    h = (day + ((13 * (month + 1)) // 5) + K + (K // 4) + (J // 4) - (2 * J)) % 7
    return (h + 5) % 7

if __name__ == "__main__":
    main()