If you use a century designation as an adjective please hyphenate it.

Some of you probably didn’t even know this was a question.

It looks like this: seventeenth-century jordans

Hyphenation still applies if you write the century numerically: 17th-century jordans

If you’re able to be more specific you’ll need another hyphen: mid-seventeenth-century jordans

But there’s no hyphen if you’re referring to a time period: jordans in the seventeenth century

For more on hyphens check out pages 375-84 in the Chicago Manual Of Style, 16th edition (or see the CMS’s online hyphenation table).