virtual iter_type do_get_year(iter_type first, iter_type last,
ios_base& x, ios_base::iostate& st, tm *pt) const;The virtual protected member function endeavors to match sequential elements beginning at first in the sequence
[first, last) until it has recognized a complete, nonempty year input field. If successful, it converts this field to its
equivalent value as the component tm::tm_year, and stores the result in pt->tm_year. It returns an iterator
designating the first element beyond the year input field. Otherwise, the function sets ios_base::failbit in st. It
returns an iterator designating the first element beyond any prefix of a valid year input field. In either case, if the return
value equals last, the function sets ios_base::eofbit in st.
The year input field is a sequence of decimal digits whose corresponding numeric value must be in the range [1900, 2036). The stored value is this value minus 1900. In this implementation, a numeric value in the range [0, 136) is also permissible. It is stored unchanged.