In Spanish we don’t use capital letters for the days of the weeks nor the months. With the exception of official documents, the date (fecha), will always follow this sequence: day, month, year.  If you are going to indicate the date in numbers only, the most recommended format would be: 5.7.17 or  2-9-2017. If you are going to write the date, this would be the most used: 17 de mayo de 2017. (preposition “de”, used in between).