A section on vacation certificates reads: "Expiration: Book this vacation by <date>." This date refers to the deadline to book the vacation, not the timeframe during which travel must take place.
Rather, travel must take place during the timeframe listed under "Valid Dates" (e.g., ("Valid May through September"). Some vacation and cruise providers may place additional restrictions on when travel may take place (e.g., "Travel must take place within 12 months of the certificate being issued"). This will be noted on the promotional flyer and issued certificate.
Keywords: expiration, experience, deadline, period, time