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This seems to be a problem date. As documented, plistlib converts plist dates to/from Python datetime.datetime objects. And, as is documented from datetime objects, the year field must be between 1 (MINYEAR) and 9999 (MAXYEAR). So, it would appear that dates with year 0 are not representable as datetime objects; it's not obvious to me how plistlib could handle a date like that without changing the API, i.e. returning something other than a datetime object or by changing the rules for datetime objects, which is very unlikely to happen.
https://docs.python.org/dev/library/plistlib.html
https://docs.python.org/dev/library/datetime.html#datetime.MINYEAR