- [[NICT]] - NTP メモ -- http://www.rr.iij4u.or.jp/~zubora/ntpcook-20070413-1.pdf ([http://www.awm.jp/~yoya/cache/www.rr.iij4u.or.jp/~zubora/ntpcook-20070413-1.pdf cache]) - 閏秒 ([[LeapSecond]])