4 - String: test cases for numerical conversion
5 - String: Implement String != regex operator
6 - String: index and rindex methods with String argument
8 - date: test parser for invalid dates and syntax errors
9 - date: Parser for stream input
10 - date: Yearday, Weekday and week number
12 - UTC: Convert to and from time_t, struct tm
14 - Add classes: configuration, amount