Makes array of dates where (day + month + last_two_digits_of_year) and number of days since Jan 1, 1970 have both been prime since Jan 1, 1970

amazon_prime_day.rb

# Makes array of dates where (day + month + last_two_digits_of_year) and number of days since Jan 1, 1970 have both been prime since Jan 1, 1970
require 'prime'
require 'date'

def date_to_sum(date)
    date.month + date.day + date.year.to_s[2..-1].to_i
end


date_to_go_up_to = Date.parse("2017-01-01")

first_day = Date.parse('1970-01-01')

this_day = first_day
days_since_jan_1_70 = 0
days_it_happened = []

while this_day <= date_to_go_up_to
    if Prime.prime?(days_since_jan_1_70) && Prime.prime?(date_to_sum(this_day))
        puts "it happened on #{this_day.to_s} because #{days_since_jan_1_70} and #{date_to_sum(this_day)} are both prime numbers."
        days_it_happened << this_day 
    end
    this_day = this_day + 1
    days_since_jan_1_70 = days_since_jan_1_70 + 1
end

puts "Between #{first_day} and #{date_to_go_up_to}, there were #{days_it_happened.size} 'prime days'."