Why does february have 28 days?

The short answer is: Roman superstition and calendar politics! The original Roman calendar had 10 months and winter was just an unassigned period. When January and February were added around 713 BCE, February got the short end with 28 days. The Romans considered even numbers unlucky, so most months had odd-numbered days. Since February was the month of purification rituals and honoring the dead, they were fine with it having an "unlucky" even number. Later, when Julius Caesar reformed the calendar, he kept February at 28 days but added the leap year every four years to sync with the solar year.

It's actually more complicated than most people realize! The original Roman calendar was based on moon cycles (about 29.5 days). When King Numa Pompilius added January and February, the calendar needed to total 355 days to match the lunar year. Since the Romans thought even numbers were bad luck, most months got 29 or 31 days. February, being the last month and dedicated to underworld gods, got the leftover 28 days - the only even-numbered month. The fascinating part is that February was originally even shorter - it had 23 or 24 days with a variable month added periodically! The History Channel has a good article on this if you want more details.