Thursday, June 21st is the summer solstice in the Northern Hemisphere, and if you’re feeling a little happier at the end of the week, science may be able to explain why. The summer solstice could actually be one of the happiest days of the year, and it’s all thanks to that sweet, sweet sunshine.

Philip Gehrman, associate director of the Behavioral Sleep Medicine Program at the University of Pennsylvania, told TIME last year that people are generally more cheerful in the summertime. Because light is the strongest cue when it comes to the body regulating circadian rhythms like the sleep cycle and hormonal fluctuations, more light is generally a good thing when it comes to improving your mood.

summer sun sunshine happy
I got that summertime, summertime...gladness?

When it comes to the amount of daylight, Thursday will be the longest day of the year, the Weather Channel reported. Since more light can elevate your mood and “entrain” your circadian rhythm, according to TIME, it makes sense that the day with the most sunlight is also a day that a lot of people may feel very happy.

The circadian rhythm is aligned better with natural sunlight and darkness, and since you might wake up while it’s still dark outside in the winter, the circadian system often doesn’t have as much of a chance to stimulate “wakefulness and improved mood” then, according to Frank Scheer, director of the Medical Chronobiology Program at Brigham and Women’s Hospital who also spoke with TIME.

So exactly how much sunshine are you going to experience on Thursday that you should take advantage of if you’re looking to cheer up a little? That all depends on your latitude, or distance from the equator, according to The Washington Post.

Summertime, baby.

Washington, D.C., for instance, will see 14 hours and 54 minutes of daylight on June 21st, AKA summer solstice. In New York, the same day will be 5 hours, 50 minutes longer when it comes to daylight than it is for December solstice.

Of course, everyone is different, and the sun isn’t the only deciding factor when it comes to your happiness. But there’s a good chance that all that sunshine might just improve your mood, so get out and enjoy it while you can because the days are only going to get shorter again after Thursday.