This article is from the Calendars FAQ, by Claus Tondering firstname.lastname@example.org with numerous contributions by others.
The answer to this question depends on what you mean by "correct".
Different countries have different customs.
Most countries use a day-month-year format, such as:
25.12.1998 25/12/1998 25/12-1998 25.XII.1998
In the U.S.A. a month-day-year format is common:
International standard ISO-8601 mandates a year-month-day format,
namely either 1998-12-25 or 19981225. This format is gaining
popularity in some countries.
In all of these systems, the first two digits of the year are
25.12.98 12/25/98 98-12-25
This confusion leads to misunderstandings. What is 02-03-04? To most
people it is 2 Mar 2004; to an American it is 3 Feb 2004; and to a
person using the international standard it would be 4 Mar 2002.
If you want to be sure that people understand you, I recommend that
* write the month with letters instead of numbers, and
* write the years as 4-digit numbers.