Some feeds are using non-standard date formats.
For example, today's date could be specified as both 17-10-16 (d-m-y) and 16-10-17 (y-m-d), depending on the host.
How to specify a custom date format as source/input format?
Currently I'm handling this issue externally, re-parsing the dates for specific feeds, but when source date includes months and weekdays in a local language, everything gets a lot more complicated...
There is no way doing this in the current version (1.4.x), so consider this an feature request.
Simplepie already handles translations internally, so I guess it makes more sense to implement it, than handling the whole date-parsing process externally.