National Key Lime Pie Day: September 26

National Key Lime Pie Day is September 26, every year. It is a popular food-day observance, not a federal holiday. You can bake the pie that day or any time you have Key limes or a good bottled Key lime juice.

The filling people mean when they say “key lime pie” is Key lime juice, sweetened condensed milk, and egg yolks. The crust is often graham cracker and butter now; older Key West recipes more often used a pastry shell. Toppings have included nothing, whipped cream, or meringue for a long time.

The Key lime is small, rounder than a regular lime, thinner-skinned, and more aromatic, and it is often more yellow than green when fully ripe. The ordinary lime in most U.S. grocery stores is the Persian lime: larger, thicker-skinned, and usually sold deep green. Persian limes make a decent lime pie, but they are less floral and a bit less sharp than Key limes.

The Florida Department of Agriculture and Consumer Services says Florida Key limes are harvested June through September, with some fruit available all year. Fresh Key limes can still be uneven in stores outside that window; bottled Key lime juice is a common substitute when the label actually says Key lime. Florida Department of Agriculture and Consumer Services, Florida Key Lime.

The filling is egg yolks, sweetened condensed milk, and Key lime juice. Ripe Key limes are often more yellow than green, and the juice is pale, so the yolks set the color. A bright-green pie usually has food coloring. The official Florida Keys tourism guide says the yolks give the pie a yellowish color and that lime-green pies are not authentic. Source: Florida Keys & Key West, Sweet Key Lime Pie Flavors the Keys.