ISO 4031 explained

ISO 4031 is a superseded international standard first issued in 1978 by the International Organization for Standardization. It defined the representation of local time differentials, commonly referred to as time zones. It has since been superseded by ISO 8601.[1] This newer standard has set out the formats for local time differentials since 1988, so ISO 4031 is no longer in use.

References

  1. Web site: ISO 8601:2004(E). 2006-11-15. 2004-12-01. ISO. Technical Committee ISO/TC 154, Processes, data elements and documents in commerce, industry and administration.. Annex A … From that concept representations of all other date and time values were logically derived; thus, ISO 2014, ISO 3307 and ISO 4031 have been superseded..