Have you ever felt bad for February? It's definitely the odd one out of the months with only 28, and sometimes 29, days. But why does it only have (usually) 28 days? Did someone just miscount in the beginning and no one along the way ever mentioned it? Turns out the decision to give make February a shorter month goes back to the Roman Empire, when people used the Romulan Calendar to keep track of days and months. The Romulan Calendar was based on the lunar cycles but only counted 10 months, leaving out the time from December until March because most Romans were too busy trying to survive the harsh winters to worry about figuring out the date. They would simply start the new year up again on the first new moon before the spring equinox.
But that only worked for so long, so then Rome's second king, Numa Pompilius, decided to create his own system, based on auspicious numbers and the desire to have 12 lunar cycles. The outcome of this ended up giving every other month 29 and 31 days; but because February was a month for purification, it got 28. However, there was an obvious problem with this: the days of the year didn't actually complete Earth's orbit around the sun, so it wasn't a full year, which meant that after a few years, the seasons didn't line up with the months and everything got even more confusing.
Flash forward to 46 B.C. when Julius Cesar, who had been traveling through Egypt, decided he liked the Egyptian calendar system, which was based on 365 days, better. It was at this time that Rome switched from a lunar calendar to a solar calendar and to account for the extra quarter of a day we eventually ended up with the leap day system we have now!