Today is January 14, 2019, according to the Gregorian calendar that you are likely to use, but in the Julian calendar this is the start of a new year.
The Julian calendar was introduced by Julius Caesar in 46 B.C. The Gregorian January 14, 2019 is January 1 in the Julian calendar. So, today is the Julian New Year, also known as the Old New Year or the Orthodox New Year. The Christian Eastern Orthodox Church still uses the Julian calendar.
The Julian calendar was used worldwide for over 16 centuries. Not a bad run.
Another place that you will still see the Julian calendar used is with the dates of astronomical events that occurred before the introduction of the Gregorian calendar in 1582.
The date for the introduction of the Julian calendar was October 15, 1582 but, as you might guess, introducing a new calendar to the world could not really happen overnight. England kept the Julian calendar for another two centuries.
It was Pope Gregory who decreed that October 4, 1582 on the Julian calendar would be followed by October 15, 1582. That means that in 1582, there was no October 5 through 14. Strange days.