The drinking age in this province is 18.
A few years ago, the Alberta Government decided that it would privatize its liquor distribution and retail system, first with wine stores and lastly the beer and wine stores (of course it kept the easy to administer importation and warehousing for itself).
The most obvious difference is liquor stores on all major intersections (does it look like on US television?). The liquor stores today (if you're used to the government-run systems in most other provinces) are becoming specialized and service-oriented. For large orders (the company party) they'll deliver (they'll even offer competitive quotes). You can select a case of your favorite micro-brewery or imported beer, and find it already cooled to the right temperature. Specialty wine stores are everywhere, and the staff will actually recommend the best wine for your planned dinner. And if they don't have it, they might even special-order it for you. Sometimes, you'll even see liquor or wine on sale!
Calgary has a wide variety of beer, wine and liquor stores. There might be one (or more) right in your neighbourhood, but the best selection and price may require a little more looking. Take the time to find one that has the items you like, or is willing to order them for you.