七旬

七旬	qī xún	70 years; one's seventies / 70 days
七	qī	seven / 7
旬	xún	(bound form) ten-day period; one of the three ten-day divisions of a month (e.g. 上旬) / (bound form) ten years (in age expressions, e.g. 六旬 "sixty years old")