Census Calculator

#Garland R. Joseph | garland.joseph@gmail.com
#October 10, 2025
# This program will input a 4-digit year and then relate
# the generations of your ancestors
# to the particular United States Census

import math
from datetime import datetime

def calculate_ancestral_census(birth_year, generations, generation_length=30):
    """
    Calculate ancestral census information based on birth year and generations.

    Args:
        birth_year (int): The birth year of the starting person
        generations (int): Number of generations to calculate back
        generation_length (int): Average years per generation (default: 30)

    Returns:
        list: List of dictionaries containing ancestral census data
    """

    current_year = datetime.now().year

    if birth_year < 1700 or birth_year > current_year:
        raise ValueError(f"Birth year must be between 1700 and {current_year}")

    if generations < 1 or generations > 10:
        raise ValueError("Generations must be between 1 and 10")

    if generation_length < 20 or generation_length > 40:
        raise ValueError("Generation length must be between 20 and 40 years")

    results = []

    for gen in range(1, generations + 1):
        ancestor_birth = birth_year - (gen * generation_length)
        first_census = math.ceil((ancestor_birth + 1) / 10) * 10
        age_in_census = first_census - ancestor_birth

        if gen == 1:
            relationship = "Parent"
        elif gen == 2:
            relationship = "Grandparent"
        elif gen == 3:
            relationship = "Great-Grandparent"
        else:
            relationship = f"{gen-1}x Great-Grandparent"

        notes = []
        if first_census < 1790:
            notes.append("Before first US census")
        elif first_census < 1850:
            notes.append("Pre-1850: Only head of household named")
        elif first_census == 1890:
            notes.append("1890 Census mostly destroyed by fire")
        elif first_census == 1950:
            notes.append("1950 Census is most recently available")
        elif first_census > 1950:
            notes.append("Census not yet publicly available (72-year rule)")

        results.append({
            'generation': gen,
            'relationship': relationship,
            'approx_birth_year': ancestor_birth,
            'first_census': first_census,
            'age_in_census': age_in_census,
            'notes': notes
        })

    return results


def display_results(birth_year, generations, generation_length, results):
    """Display the results in a formatted table."""
    print("\n" + "="*80)
    print(f"ANCESTRAL CENSUS CALCULATOR")
    print(f"Starting Birth Year: {birth_year}")
    print(f"Generations: {generations} | Generation Length: {generation_length} years")
    print("="*80)
    print(f"\n{'Gen':<4} {'Relationship':<20} {'Approx Birth':<14} {'First Census':<12} {'Age':<6} Notes")
    print("-" * 80)
    for result in results:
        notes = "; ".join(result['notes']) if result['notes'] else ""
        print(f"{result['generation']:<4} {result['relationship']:<20} {result['approx_birth_year']:<14} {result['first_census']:<12} {result['age_in_census']:<6} {notes}")


def main():
    """Main function to run the ancestral census calculator."""
    print("ANCESTRAL CENSUS CALCULATOR")
    print("Calculates when ancestors appear in US census records.")
    print("-" * 60)
    try:
        birth_year = int(input("Enter the starting birth year (e.g., 1962): "))
        generations = int(input("Enter number of generations to calculate (1-10): "))
        use_default = input("Use default 30-year generation length? (y/n): ").lower().strip()
        generation_length = 30 if use_default == 'y' else int(input("Enter generation length (20-40): "))
        results = calculate_ancestral_census(birth_year, generations, generation_length)
        display_results(birth_year, generations, generation_length, results)
    except ValueError as e:
        print(f"Error: {e}")


if __name__ == "__main__":
    main()