Project Euler 19 in ruby

months_table =
{
  1 => 0,
  2 => 3,
  3 => 3,
  4 => 6,
  5 => 1,
  6 => 4,
  7 => 6,
  8 => 2,
  9 => 5,
  10 => 0,
  11 => 3,
  12 => 5
}

leap_table =
{
  1 => 6,
  2 => 2,
  3 => 3,
  4 => 6,
  5 => 1,
  6 => 4,
  7 => 6,
  8 => 2,
  9 => 5,
  10 => 0,
  11 => 3,
  12 => 5
}

sundays = 0

first_day = 0

# From 1901 to 1999

1.upto(99) do |year|
  1.upto(12) do |month|
    if year % 4 == 0 # leap
      table = leap_table
    else
      table = months_table
    end
    if (first_day + year + (year / 4) + table[month] + 1) % 7 == 0
      sundays += 1
    end
  end
end

# 2000 which starts with 6

first_day = 6
year = 0

1.upto(12) do |month|
  if (first_day + year + (year / 4) + leap_table[month] + 1) % 7 == 0
    sundays += 1
  end
end