Dates in Spanish can be spelled out in their entirety, written in a combination of letters and numbers, or only with numbers:
a) It is not common for dates to be expressed completely in words: Veintiocho de septiembre de mil novecientos noventa y seis. This generally only happens in very official documents, public decrees, notarial acts, or checks. The first day of a month can be written out as primero, which is more common in Latin America, or as uno, which is more common in Spain.
b)The system that is most widely used combines words and numbers: the day and year are written with Arabic numerals and the month is written out, with the first letter in lowercase: 12 de octubre de 1492. In ancient documents, writers frequently used Roman numerals, at times in lowercase, to indicates the day and year. These days it is common to represent years with Roman numerals on monuments or commemorative plaques, and always in upper case.
c) It is quite common to abbreviate dates by writing them in number form and separating the numbers related to the day, month, and year with dashes, slashes, or periods. They are written without spaces separating the numbers: 28-8-98; 16/III/1971; 8.6.00. The year can be written in full, with all four numbers of the year, or with only the final two. The month can be represented with Arabic or Roman numerals. When the number representing the month or day is lower than ten, it is recommended to omit the zero, unless it is necessary for technical (for example, in computerized reports) or safety (to avoid changes to the date in financial or commercial documents) reasons; this means that it is preferable to write 5.7.99 or 2-9-1940 as opposed to 05.07.99, 02-09-1940.