Historical clue formulations

• Dating app distance metric — 2019-07-07
• Wheel spoke, essentially — 2017-09-20
• Figure that's squared in a common formula — 2007-11-13
• The "r" of "pi r squared" — 2004-12-20
• Distance on a radar screen — 1997-05-28
• Range of operation — 1995-10-08