Marijuana enthusiasts won’t have to take a sick day this year, as 4/20, the annual cannabis holiday, conveniently falls on a Sunday. That means today is essentially the Black Friday of marijuana in Colorado, which legalized recreational pot in 2012 and started a market for it this year (Colorado has long had medical marijuana).

But it seems every Friday is significant to Colorado pot smokers.

MMJ Menu, a point-of-sale system owned by Weedmaps, provided us with anonymized pricing and sales data from about 83 medical dispensaries and 15 recreational dispensaries in Colorado that use the MMJ Menu system. We’ve only just begun to tap into this resource, but with 4/20 approaching, we wanted to find out when people buy their weed.

The MMJ Menu data doesn’t account for the entire market — Weedmaps lists 451 dispensaries in Colorado — but it’s a solid sample of dispensaries in the state (for example, medical marijuana dispensaries represent almost the entire data set, because they make up most of the legal weed market in Colorado).

We found the aggregate cannabis flower sales (in pounds) for each day in the data set, which covers Jan. 1 to early April. Then we looked at which days of the week had the highest average aggregate sales. Here’s what we saw (figures are rounded):

The medical sales, you’ll see, are an order of magnitude larger than the recreational sales. Indeed, medical cannabis dominates the state’s pot market; many Colorado smokers probably had a medical card pre-recreational legalization, so the vast majority of sales remain medical.

Still, when comparing days of the week, we get a solid picture of what Coloradans are doing. Fridays and Saturdays — perhaps not surprisingly — appear to be the most popular days to buy weed.

Correction (April 18, 9:20 a.m.): An earlier version of this post misstated the number of Colorado dispensaries in the MMJ Menu dataset. The data was pulled from 83 medical dispensaries and 15 recreational dispensaries.