International Date Format ISO 8601
where CC is the century (representing the digits used in the thousands and hundreds components, as opposed to the actual century), YY is the year, MM is the month of the year between 01 (January) and 12 (December), and DD is the day of the month between 01 and 28 or 29 or 30 or 31, depending on length of month and whether it is a leap year. These dates are using the Gregorian calendar.
For example : 1998-01-15 is the fifteenth of January in the year nineteen ninetyeight A.D. - completely unambiguous
This notation is language independent - a true international standard from the International Organisation for Standardisation .