A lot of debate has been going on about Elsa’s birthday. It is generally agreed upon that Elsa is born in late December 1821. But dozens of sources cannot agree on whether it is December 21st or 22nd.
The only person who can give us a definite answer on Elsa’s birthday would be her mother Iduna, but since she is fictional and very much dead, we must turn to her “creative mother”, Jennifer Lee.
Unfortunately, Jennifer only gave us the slightly cryptic explanation that Elsa was born on the Winter Solstice.

So, naturally, everybody was quick to check when exactly is the Winter Solstice. Well, it depends… It is generally on December 21st or December 22nd, depending on the year.
So, the next course of action was to check when exactly the Winter Solstice was in 1821, the year when Elsa was born. And Winter Solstice 1821 was on…

So that it’s then, right? Elsa is born on December 21st!
Wait a second, not so fast. We are not there yet. If you look closely at the picture above, you’ll notice that this Winter Solstice date is for Burbank, United States, where the Disney Animation Studios are located.
Now, if Elsa had been born in the United States at that very moment, she would indeed have been born on December 21st. But it is common Frozen fan knowledge that fictional Arendelle and the lives and traditions of its citizens are modelled after mostly Norway and a tiny bit of Sweden. There is even a place called Arendal in real-world Norway.
The timezone of Arendal (or the entirety of Norway for that matter) is quite a bit ahead of Burbank, USA, where the Disney Animation Studios are located. One could argue that Elsa was in fact born in the Disney Animation Studios. But if we are going to take that route then the entire story would be totally different, and she would have been born in 2008, when the first development of Frozen started at Disney or even later when Jennifer Lee decided to deviate way further from the original Snow Queen story than originally anticipated and decided to create Elsa instead.
So, back to the beginning to cut a long story short. [Well, it’s a bit too late for that now, isn’t it? – Ed] When was the winter solstice in 1821 in Norway?

Elsa was born on December 22nd 1821!
The fact that many believe it would be the 21st is most likely because most of the content about the Frozen franchise originates from the United States and yes, at the very moment that Elsa was born it was still December 21st over there.
So there you are. Feel free to disagree, but December 22nd is the date that we’re going to stick with on this website anyway unless somebody comes up with an excellent argument why that is incorrect.