Historical clue formulations

• When doubled, a Billy Idol #1 hit — 2014-05-07
• With 70-Across, #1 hit for Billy Idol — 2013-10-08
• When doubled, a #3 hit of 1968 or a #1 hit of 1987 — 2010-05-06
• When repeated, a Billy Idol hit — 2009-06-03
• When repeated, a top five hit of 1968 or 1987 — 2006-11-05
• When repeated, a 1968 pop hit — 1996-07-12