Here is how it works. The Ethiopian calendar has 12 months that are each exactly 30 days long. That is only 360 days - and a year is actually 365 (or 366) days. So Ethiopia has a tiny 13th month, called Pagume, that lasts just 5 days (or 6 days in a leap year).
It is a beautifully tidy idea. Imagine if every month in your calendar had the same number of days. You'd never have to remember whether September had 30 days or 31, because they'd all be 30. The leftover days at the end of the year are saved up in tiny month 13.
Ethiopia is also about seven and a half years behind the rest of the world. That is not because anything is wrong - it is just that the Ethiopian church calculated the start of the year of Jesus's birth slightly differently from the calendar most of the world uses today. So when most countries say it is 2026, Ethiopia says it is 2018 or 2019.
This means Ethiopia celebrates its New Year (called Enkutatash) in September, not January. Children get the day off school, families gather, and the harvest season is just beginning. It is a different rhythm to the year - one that has worked for Ethiopia for over 1,500 years.