Project Management Central

Good question, because if you see 02/09/2016, then you are not sure if it means February or September. The norm for American is February, and norm for British is September, but if we are doing global business, then it is confusing.
And I think we never see YYYY-DD-MM.
So YYYY-MM-DD has this additional advantage on top of sorting nicely!

In Canada it depends on the organization. I've seen all 3 formats here.

In the UK it is dd.mm.yy but in my project filing I use yyyymmdd (e.g. "Minutes 20160920.docx") because then it sorts nicely. I picked that tip up while working in France.

I prefer 01 Jan 2016 ('dd mmm yyyy').

It makes it unambiguous. No one has to figure out if "4/5/2016" is 5 April or 4 May. It's a good question, though. We can't assume everyone on our team uses the same default date format, especially if you have an international team.

If the dates need to be manually sorted, or if you're naming digital files by date, it's nice to have a number format from small to large (dd.mm.yyyy) or large to small (yyyy.mm.dd). For dates as data, though, you can use Excel to sort any date format, unless you work for a bureaucracy or something similar that requires multiple printed copies in triplicate.

For storing files for sorting I find the best format is YYYYMMDD.
For communicating dates, my preference is DDMMMYY, as the month in letters is clearer than a number, and although the letters vary in different languages the English abbreviation is usually well known.

Latin America: dd / mm / yyyy
If you work with organizations in other countries, the most unambiguous method is as outlined above dd - mmm - yyyy (using either dashes, slashed or dots - though in Latin America or the US I have not seen the dot used much - just in Europe)