What a year in pixels is for
A year in pixels is one square per day for a whole year, each filled with a colour that stands for how the day went. It started in bullet journals and spread because it answers a question a month cannot: what does a year of me look like?
The answer is usually more boring than people expect. Most years are mostly middling squares, with a few runs of dark ones that line up with something you already knew about: a move, a winter, a job that went wrong. Seeing that on one page is the point.