I remember receiving a post-card from a family member, who had travelled to Ethiopia, as a child and being amazed that the date was roughly 7 years behind my own and dated January 2007 at the time.
To make a long story short, the country of Ethiopia operates on a different calendar from the rest of the world, which has largely adopted the Gregorian calendar. The calendar in use in Ethiopia has a 13-month-long year and includes leap-days from time to time.
The BBC released this very interesting video at the start of 2020 which explained how different religious groups view the year, depending on how their calendar is calculated, whether it be lunar, solar or lunar-solar. Although the religious calendars may differ, most nations use the Gregorian calendar to avoid confusion... all I know is that if I ever do visit Ethiopia, I will definitely lose track of time. (Pun intended. 😉)
Are you familiar with any interesting time-warps?