Every weekend, you’re given 2 glorious days of freedom from the oppression of your corporate overlords. You adventure, you party and you nap whenever you damn please — until your playtime abruptly ends.

It’s Monday. And naturally, you’re pretty miserable about that.

Of course, you’re not alone. Monday is the most terrible day of the week for millions of people, and today science can prove that for a fact.

The evidence comes from mathematicians and scientists at the University of Vermont, who have been using a program they call the “Hedonometer” to analyze happiness sentiments on Twitter since 2008. According to the researchers’ findings, our mood plummets to pathetic depths on Mondays, then steadily rises as the weekend draws nearer. It peaks on Saturdays, then crashes again as we prepare to return to our sad little cubicles.

Analyzing data on happiness has always been difficult, but the hedonometer offers a revolutionary technique. It scans a random sample of about 50 million global Twitter posts every day, and assigns a happiness score to the most frequently used 10,000 words. Each word’s score is on an increasing happiness scale of 1-9, and the average of all words analyzed gives us a pretty good idea of each day’s level of happiness.

Happiness scores are significantly influenced by uplifting moments or tragic events. Although average daily mood is ordinarily somewhere around 6 to 6.1, on Monday of last week, the day after the deadly mass shooting in Las Vegas, happiness levels dropped to 5.7, making it the saddest day on record.

Exploring Hedonometer’s Twitter time series allows us to determine a number of other events that reduced or boosted our moods. One notable high point: International Women’s Day. One notable low point: the election of Donald Trump as US president.

In general, happiness follows some pretty simple patterns — the lows follow natural disasters, the deaths of celebrities, and terrorist attacks. The highs follows holidays and happy human developments, like the legalization of same-sex marriage.

In the future, the hedonometer can be used to determine much more than which day of the week we hate the most. Changes in legislation, in economic conditions, and in which Kardashian is pregnant can produce visible differences in our levels of happiness.

Even on a miserable Monday, that gives us something to be excited about.