Drafting Contracts: “Ten Days Notice” or “Ten Days’ Notice”
Should there be an apostrophe?
Yes, that would be the correct grammatical way of expressing this concept in a legal document.
However, this is only the case, if you are using it in a sentence.
If it were to appear in a chart, with the word “notice” omitted, then, it would simply be “ten days” under the column dealing with notices