Q. Is it possible to by an airline ticket without knowing the exact date of travel? I’m wondering if I can purchase a ticket ahead of time and decide later when I was going to fly.
A. You can always purchase an airfare and change the dates of travel, but the fare may change (either up or down) for travel on the date you decide to fly, and in most cases the cheapest fares will also require a change fee if you do decide to change dates (and you can be sure it won't come cheap!). Of course, you could buy an expensive fully-refundable fare and change the dates all you want, but I’m guessing that’s not what you had in mind.
If it suits your itinerary, there's always Southwest Airlines, which doesn’t charge a change fee. But again, the fare on your new dates of travel may be higher or lower than the fare you originally bought (you’ll either pay the difference if higher, or get a travel voucher for future travel if lower).