Are there locales or common programs that use YYYY-DD-MM as the date format?

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 int开发者_JAVA百科o 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.

yyyy-mm-dd in particular is a subset of the ISO-8601 format.

There is no recognised standard that uses year date month. When year is first, it should always be followed by an appropriate sub-year, be that quarter, month, julian day, etc.

Some advantages to using year-first is that the order also happens to work well for alpha-sorting when used as a text value (such as part of a file name).

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.

According to Wikipedia Kazakhstan may use YYYY.DD.MM. I can't read the source for this information, so I don't know the specifics.

See: https://en.wikipedia.org/wiki/Date_format_by_country

That aside, I do believe that the delimiter still makes it visibly different from YYYY-MM-DD, so there should be no issue.

Example: 2017-01-13 vs 2017.13.01

As also mentioned by @Tracker1 and @DaveE, YYYY-MM-DD is the ISO-8601 standard format.

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.