Date detection in a dynamic template

Hi guys. In the index linked to below, the dynamic template is configured
to set its properties' type to "string".

However, when indexing a document that contains a date-like value, the
dynamic property that's created has its type set to "date" instead of
"string". Why would that be?

This can be seen on lines 42-45 of the last file in this gist:

Thanks for your help!

Embarrassingly, I posted too soon. The dynamic property that's created was
having its type set to "date" instead of "string" because it was NOT
matching the dynamic template.

After adding a mapping template specifically for dates, life is peachy.