現在時刻のずれチェックするやつ

checkdatediff.rb

#!/usr/bin/env ruby

require 'date'
require 'json'
require 'net/http'

response = Net::HTTP.get URI('http://ntp-a1.nict.go.jp/cgi-bin/json')

json = JSON.parse(response)
diff = json['st'] - Time.now.to_i

if ( diff < -50 || diff > 50 )
    p '現在時刻がずれています'
    exit 1
end