devine@cookie.dec.com (Bob Devine) (09/02/88)
> What ISO standard exists for representation of time? > Could some one please summarize the standard? There are 3 ISO relevant standards: 2014, 3307, and 4031. ISO 2014 Writing of calendar dates in all-numeric form This says that when writing a date just using numbers, the year is first and has 4 digits (though 2 digits can be use if "no possible confusion can arise from the omission of the century"), the month is next with 2 digits, and the day is last with 2 digits. The example given in the standard is for July 1, 1976. There are 3 legal representations: 1. 19760701 2. 1976-07-01 3. 1976 07 01 ISO 3307 Representation of time of the day This one is complicated! From the standard: "Local time of the day is defined as clock time in public use at the point of origin. In the 24-hour timekeeping-system, local time of the day may be expressed by the following combinations of the time elements hours, minutes, and seconds: a) hours b) hours and decimal fraction of an hour c) hours and minutes d) hours, minutes and decimal fraction of a minute e) hours, minutes and seconds f) hours, minutes, seconds and decimal fraction of a second" So, one could choose what precision is needed and then use the appropriate combination. There is also the need to allow the separators between the fields (there are colons, commas, periods, or nothing depending on the fields). ISO 4031 Representation of local time differentials This uses the ISO 3307 standard as a base and adds a suffix to identify the difference from UTC. That is, it is time-of-day plus +hhmm where the '+' could also be a '-' to indicate subtraction and the hhmm is the time difference in hours and minutes from UTC. For example, here in the Mountain Time zone, the suffix of -0700 is used because we are west of the Greenwich Meridian. You also might want to look at the working being done for OSI, specifically the X.400 data types. There are two types defined for date-time that use the above ISO standards to compose a single character string representation. Both are restrictions on the many different options (ie, dash or space or nothing) and provide a method to encode the date-time with sufficient precision for nearly every use. Bob Devine DEC Database Systems in Colorado Springs