possessives - Apostrophes in Time Expressions

Are these expressions syntactically correct and semantically equivalent? What is general rules for "number-time noun" and "number time' noun" from semantic point of view?

• "a day's work" vs "one-day work"


• "two days' notice" vs "two-day notice"


• "one year's pay" vs "one-year pay"

also see here.