Large year values are not parsed correctly #160
Description
If the year value is larger then 9999, the parsing result is inconsistent with GNU implementation:
Input: 10000-12-31
GNU: 10000-12-31 00:00:00+00:00
parse_datetime: 0000-12-31 00:00:00+00:00
Input: 100000-12-31
GNU: 100000-12-31 00:00:00+00:00
parse_datetime: 2000-12-31 00:00:00+00:00
Input: 1000000-12-31
GNU: 1000000-12-31 00:00:00+00:00
parse_datetime: 0000-12-31 00:00:00+00:00
Input: 10000000-12-31
GNU: 10000000-12-31 00:00:00+00:00
parse_datetime: Invalid input string: cannot be parsed as a relative time
Input: 2147485547-12-31
GNU: 2147485547-12-31 00:00:00+00:00 // This is the max value supported by GNU
parse_datetime: Invalid input string: cannot be parsed as a relative time