system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come September, October, November, December are the 9th-12th months respectively, when their names suggest they should be the 7th-10th?
gpt
Originally the Roman calendar started in March and had ten months, so the names matched up with their position in the year. After December were 51 days of winter which weren't part of any month, then March came round again. When January and February were added to fill in those extra days, January became the first month but the other months kept their names.