Also, date format strings are pretty standard. If you ever forget them, just type `man strftime` at the command line.
Removing unneeded abstractions is positive, specially if you have to deal with conflicting models.
Or perhaps force the choice of a particular (memorable) date-time, such as January 2nd, 2000, 3:04 am and 5 seconds?
If you can't unambiguously determine the format from the example, kick it back to the user and ask for a better example. Easy peasy. As it turns out, users are incentivized to give good examples because they want to get work done. They won't provide "01-01-01" as an example unless they want to waste their own time.