Each submission must be a full program.
The program must take input as two comma-separated dates in the form
YYYY-MM-DD, and print the number of days that has passed since the second date to STDOUT as if today was the first date (if the second date would be in the future, output a negative number) plus an optional trailing newline, and nothing else. Assume both dates are in the Gregorian calendar.
The program must not write anything to STDERR.
Note that there must be an interpreter so the submission can be tested.
Submissions are scored in bytes, in an appropriate (pre-existing) encoding, usually (but not necessarily) UTF-8. Some languages, like Folders, are a bit tricky to score - if in doubt, please ask on Meta.
This is code-golf, so shortest code wins