To honor the 50th anniversary of the drink, McDonald’s is making it available for purchase throughout the United States starting today (2/19)

In the interests of full disclosure, I must admit that I haven't had a Shamrock Shake in close to 20 years. I didn't even know that it’s been three years since the shake was last sold nationally.

McDonald’s first started selling the drink in 1970. Over the years, the burger chain has brought back the original as well as variations of the shake, like a “Shamrock Sundae” in 1980 and a chocolate version in 2017. It first started selling the item nationally in 2012.

In addition to the traditional green vanilla shake, McDonald’s is selling a version made with Oreo cookies. Both drinks will be sold for a limited time.

WGN-TV News on why you can't get one year round:

For fast food chains, which are constantly competing for customers’ dollars and attention, specialty offerings are a way to try to cut through the noise and give people a reason to visit stores.

Plus, seasonal offerings help get customers in the habit of coming in at a certain time of year. Ideally for the company, people will associate fall with Starbucks’ Pumpkin Spice Lattes, or early spring with a Shamrock Shake.

Chains are unlikely to add these types of items to their regular menus because they’re such an important marketing tool.

Plus, while people get excited for Pumpkin Spice or Shamrock Shake season, they may not actually want the indulgent items all year round.

Don't feel like going out for one? Try this: