Historical clue formulations

• Like our standard number system — 2024-05-22
• Something you can count on? — 2021-03-19
• Decimal — 2020-08-28
• Decimal system — 2018-04-25
• The decimal system — 2017-05-30
• Decimal system — 2010-08-15
• Common thing to count in — 2009-05-24