Time::Duration::ja で human-readable な経過時間を表示 - end0tknrのkipple - web写経開発
以前、別のエントリで、perl のTime::Duration::ja を紹介していますが、これのjquery版と言えるjQuery EasyDateを見つけました。
表示される単位も次のように定義されているので、i18nも簡単かも
$.easydate.locales.enUS = { "future_format": "%s %t", "past_format": "%t %s", "second": "second", "seconds": "seconds", "minute": "minute", "minutes": "minutes", "hour": "hour", "hours": "hours", "day": "day", "days": "days", "week": "week", "weeks": "weeks", "month": "month", "months": "months", "year": "year", "years": "years", "yesterday": "yesterday", "tomorrow": "tomorrow", "now": "just now", "ago": "ago", "in": "in" };