1. In most countries of the world, dates are written in order DAY/MONTH/YEAR, e.g., 4 July 1999, abbreviated 4/7/1999.
2. In eastern Asia, however, dates are written in order YEAR/MONTH/DAY: 1999 July 4, abbreviated 1999/7/4.
3. The first system (DAY/MONTH/YEAR) is much more widespread, although it could be argued that the second (YEAR/MONTH/DAY) is at least as rational (i.e., hours, minutes, and seconds are written in descending order, so why not years, months, and days too?).
4. In the USA, dates are recorded in most communication in an irrational order: MONTH/DAY/YEAR, written July 4, 1999 and abbreviated 7/4/1999. The USA seems to be the only country with this weird system.
5. Strunk and White (1979. The Elements of Style) argue that the order "4 July 1999" is better than the order "July 4, 1999" because no comma is necessary when the digits of day and year are separated by the letters of the name of the month.
6. The U.S. military, which cannot afford international misunderstanding, writes dates in DAY/MONTH/YEAR order as 4 JUL 1999. The U.S. Immigration and Naturalization Service now requires airline passengers arriving from abroad to fill out forms with dates written in DAY/MONTH/YEAR order.
7. All the scientific journals (including publications of the Entomological Society of America and the Florida Entomological Society) that follow the Style Manual of the Council of Biological Editors require that dates be written in order DAY/MONTH/YEAR, as 4 July 1999, abbreviated as 4 JUL 1999 or as 4-VII-1999*.
*The last abbreviation above requires use of Roman numerals: I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII for the 12 months.
8. All your scientific manuscripts should have dates in order DAY/MONTH/YEAR. All your abbreviations of dates in manuscripts or on specimen labels should be written in order DAY/MONTH/YEAR as 4 JUL 1999 or as 4-VII-1999.
References:
Council of Biological Editors. 1994. Scientific Style and Format. The CBE Manual for Authors, Editors, and Publishers. Cambridge Univ. Press; Cambridge, UK. 6th edition.
Strunk, W., White, E.B. 1979. The Elements of Style. Macmillan; New York. 3rd. edn.