Please keep your political discussion off chapter comments.
If you're so keen on discussing about it, go and do it there instead: https://mangadex.org/thread/260818
And finally the reason behind the name of the series has been revealed. "Seifuku", Uniform.
If it had been the English word Uniform, it could've been a pun of Yuunagi's name.
The "Yuu" sounds a bit similar to the "U" in Uniform, especially when spoken with a Japanese dialect.
"The real life version of this holiday is in April"
No, the solstices are in June and December.
The equinoxes are in March and September.
Why did you think the winter solstice is in April?