the roman year started on march 1 so thats how they numbered months. English never caught up.
The Roman year originally started in March (the month of Mars) because that’s when the war season started. January and February were at the end of the year and originally weren’t named at all.
But at some point, the Romans had a problem with one of their politicians. He had a one year term. To get rid of him, they moved the new year to January. It was supposed to be temporary but somehow we’re still living with the results of that lifehack.