BUT Why does February have only 28 or 29 days?

It’s a short month because of a battle of egos between two Roman emperors.

When Augustus Caesar came to power he decided to name a month after himself and changed Sextilis to Augustus (our August).

The preceding month Julius (our July, named after his uncle) had 31 days.

Not to be outdone, Augustus gave his own month (August) 31 days.

This meant another month had to lose a day, so Februarius (our February) was cut to 28 days.

It got an extra day every four years in an attempt to keep in step with the seasons.