RoR: Determining two date within the acceptable range

There are two dates where the first date is greater or equal to (gteq) and the second date is less than or equal to (lteq). Both dates set to have a rule where it must be within 3 months range. As always, there are always many ways to determine the range of between gteq and lteq. We will discuss three (3) solutions for this case where the third solution is the best way to consider.