I just noticed this. Hover over a bounty end period and you get:
but normally it's:
I'm sure it's just a minor oversight and a really simple fix.
Agreed; the M/D/YYYY format here is ambiguous with the D/M/YYYY format that is common outside the US. The ISO 8601 YYYY-MM-DD date format should be used. It looks like this one was missed as part of this fix.