You should check out the answer here:
ToLocaleDateString() changes in IE11
You shouldn't be using a function intended to format something for locale-specific human display and expect the output to be machine parsable. Any of the output of toLocaleString, toLocaleDateString, or toLocaleTimeString are meant for human-readable display only. (As Bergi clarified in comments, toString is also meant for human display, but ECMA §15.9.4.2 says it should round-trip)
Although the function returns a string, it's only human-readable and is never appropriate for machine parsing. I'm not 100% sure what encoding it is for IE, but although it looks like a string, underneath it uses a different encoding.
For date formatting, you may wish to use Moment.js, or just write your own formatting function.