09-260 To: J3 From: Robert Corbett Subject: Normative Reference to ISO 8601:1988 Date: 2009 July 24 References: 09-007r2 1. Introduction -- ------------ The normative reference to ISO 8601:1988 [2:6-7] is out-of-date. ISO 8601 has been revised twice since 1988. Because the reference is dated, the 1988 edition, which was the first edition, is the edition that applies to the Fortran standard. The first edition of ISO 8601 was a flawed standard. Before it was emended in 1991, it required minutes and seconds to be numbered from 1 to 60 and hours to be numbered from 1 to 24. Even after emendation, it makes no provision for leap seconds. The second edition of ISO 8601 fixed the serious flaws. I have not read the third edition of ISO 8601, but I know it was supposed to be a full revision of the standard. The claims made in Note 13.9 [343:3+] are not correct. The instrinsic subroutine DATE_AND_TIME provides for leap seconds, while ISO 8601:1988 does not. Therefore, they are not compatible. ISO 8601 (any edition) is not the defining document for UTC. ISO 8601:1988 contains a definition of UTC, but it does not define UTC. The definition of UTC given in ISO 8601:1988 was out-of-date before the standard was first published. ISO 8601:1988 based its definition of UTC on ITU-R Recommendation TF.460-2, Standard Frequency and Time-signal Emissions. ITR-R Recommendation TF.460-4, which was approved in 1986, contains a definition of UTC that is still current. 2. Discussion -- ---------- I initially thought this problem should be fixed by dropping the date from the normative reference. If that edit is made, someone should check that the latest edition ISO 8601:2004 does not contain any surprises. Over time, I concluded that ISO 8601 should not be among the normative references. The normative references are supposed to be "indispensable." ISO 8601:1988 is dispensable. I see no sign that any implementation of Fortran has been influenced by it. If the members of the committee think a definition of UTC is required, one should be added to the draft standard. The following definition is from ITU-R Recommendation TF.460-4 Coordinated Universal Time (UTC) UTC is the time scale maintained by the Bureau international des poids et mesures (BIPM), with assistance from the International Earth Rotation Service (IERS), which forms the basis of a coordinated dissemination of standard frequencies and time signals. The latest edition of ITU-R Recommendation TF.460 is ITU-R Recommendation TF.460-6. I have not read the -5 or -6 editions. 3. Edits -- ----- [2:6-7 1.2p3] Editor: Delete the paragraph. [343:3+ 13.7.44 Note 13.9] Editor: Delete the note.