Writing calendar dates correctly is important to edit your perfect formal letter (we have a quick and effective guide for that) and get the job of your dreams. I know it looks more complicated than the Maya calendar, but this quick guide will guide through the mess.
As rule of thumb, in informal writing, you can use a variety of forms, while in formal writing you should consider the person you are writing to, and choose the date format accordingly.
US-style
In the US, the date is formally and traditionally written out in the "month dd, yyyy" format. If you are writing a business letter, write it out like this:
February 23, 2016
Write it as a cardinal number, never write the ordinal form “February 23rd, 2016”. Americans pay attention to weird details and the comma, the one between the date and the year, is very important to them. If you want to write less formally, you can use the all-numeric date format (e.g. 02/23/2016 or 02/23/16). The European “dd-mm-yyyy” format has increased in usage in the US in the last decades. Even if it doesn't sound completely awkward to an American, don’t use it in a formal letter.
European-style
In Europe, we don’t have a common language and it's no surprise that we have different date formats. Don’t blame us, we love it like this! The use of the “dd/mm/yy” format (where months are not generally written out in full) is the most widespread. The European “23/02/16” would translate into the American “February 23, 2016”.
Other styles
The other common date format is the ISO 8601 standard, which uses the yyyy-mm-dd format, as in “2016-02-23”. This format is great for software, indexing and reduces the chances of error. It is also used in the US, mainly in computer applications, and not in formal letters.
If you want to write also the weekday, put it at the beginning, e.g. “Tuesday, February 23, 2016” (American way), or “ Tuesday, 23/02/16” (European way).
Ludwig's wrap-up
If this is not enough to satisfy your thirst of knowledge, please make reference to the Chicago Manual of Style
