What does a CAP date look like?

["Bob Wyman" <bob@wyman.us>]

Title: Message

    CAP specifies that dates should be in ISO 8601 format. However, ISO 8601 specifies not just one format for dates but a number of alternative formats. Unless it is the intention of the CAP authors to require that all implementers of CAP be prepared to accept any date in any of the numerous formats defined in ISO 8601, it would be useful to modify the CAP specification to explicitly state *which* ISO 8601 defined format or formats are intended to be used.

    At the simplest level, while ISO 8601 defines a number of representations for how timezone is to be represented, it does not *require* that a timezone be present in a date. This is, of course, an issue that has caused endless debate in numerous protocol and format definition groups in the past. There are those that will argue passionately that timezones MUST be provided (I am among them) and others who will argue that they should be optional. What is the position taken by CAP? In any case, some consideration should be given to how a timezone should be represented. According to ISO 8601, all of the following identify the same point in time:

    12:00Z  =  13:00+01:00  =  0700-0500

Which representation is correct for use in CAP?

 

    Also, ISO 8601 supports at least the following alternative date formats:

        20040306, 2004-03-06, 04-03-06, 040306

One can also say 2004-W01, 2004W01, or 04W01 to indicate the "first week" of 2004...

And, of course, 2004-W01-2 would indicate the second day (Tuesday) of the first week of 2004...

 

    Times in ISO 8601 are available in all sorts of forms. Thus, you can say 23:59:59.2234 or 235959.2234. And, when you form a "date/time" the "T" which separates the "date" from the "time" part is optional... Does CAP require it? If not, why not?

    Simply referring to ISO 8601 unfortunately does not result in an unambiguous definition of date/time formats unless one intends to require that all CAP implementers are prepared to implement a date/time specification which is significantly more complex then CAP itself. It would be very useful if the CAP specification were to identify the profile of ISO 8601 elements that were supported. This is the normal thing for protocol or format specifications to do.

 

        bob wyman