ISO 3166-3: Missing period of validity

The included ISO 3166-3 data currently lacks the period of validity of the deleted ISO 3166-1 entries. The included withdrawal_dates are delayed (sometimes several years as with the numeric code change of Netherlands Antilles from 532 to 530). Wikipedia for example includes a column Period of validity of the former alpha-2/3 codes (but none for the withdrawal date), ISO 3166-3 Newsletters (example) do also include a Period of validity of the former ISO 3166-1 code elements.

Note that currently, the withdrawal_date of Serbia and Montenegro (CS) is confused with the date when the last former state, Serbia, declared its independence (update: fixed via !28 (merged)).