Historical clue formulations

• Dag Hammarskjöld's successor at the U.N. — 2019-09-08
• "View From the U.N." memoirist — 2016-02-19
• Onetime U.N. leader — 2012-10-28
• World leader elected in 1961 — 2002-10-20
• Secretary General before Kurt Waldheim — 2001-02-19
• World leader, 1961-71 — 1997-08-07