I've often standardized on YYYY-MM-DD as the date format for communicating within a geographically distributed project teams to dispel any ambiguity that might arise from local date formats.
Is it likely that I might run into people who are used to seeing dates as YYYY-DD-MM? Are there programs that use this as a date format?
See "Calendar date" on Wikipedia on the topic - it lists the countries by date/time format.
At first glance it doesn't look like anyone is using YYYY-DD-MM regularly.
You should try to get your team(s) to standardize on ISO 8601 formatting, or use it and tell everyone that's what you're using. Or see Wikipedia's ISO 8601 reference.
There are none in the list of cultures in Windows that default to YYYY-DD-MM, so I would say you are pretty safe, in general, however since you can customize the dates, you should probably support it, if you want to be sure.
