[drdec]

Both the 1600s and the 17th century are 100 years long.

[ponyfleisch]

Yes, that wasn't my point. I find the term "synonymous" when used for unambiguous numerical values that are off by 1% strange. But i'm not a native english speaker.

Roughly 1% of people born in the 17th century were not born in the 1600's.