[BCP175]   Best Current Practice 175,
              <https://www.rfc-editor.org/info/bcp175>.
              At the time of writing, this BCP comprises the following:

              Lear, E. and P. Eggert, "Procedures for Maintaining the
              Time Zone Database", BCP 175, RFC 6557,
              DOI 10.17487/RFC6557, February 2012,
              <https://www.rfc-editor.org/info/rfc6557>.