Some quick thoughts:
1.) I’m not clear about item #2 under Standard Features. The label says “Date/time - without hyphen/colon.” However, the example uses hyphens: 2001-02-03T093001
2.) Hyphens: The option express to a date without a hyphen is appealing. Without the hyphen, the date looks elegantly simple. However, this option creates too much complexity. Systems will possibly have an extra format to parse. It also leads to possible data errors. How to remember it is okay to use 19990415 to represent year, month, and day, but not okay to use 199904 to represent a year and month?
3.) Further complicating the hyphen issue, it looks like section 3 only permits questionable dates to be represented without the hyphen: 20040611? Is 2004-06-11? permissible? I’m not seeing an example formatted that way. How would I represent 200406(11)? if I were a hyphen user?
4.) Unspecified years, days, and months can be represented with the letter u. From the examples: 199u, 1999-uu, 199901uu. However, when only the century is known, the letter u is not used to fill in the missing digits: 19 is used for sometime in the 20th century. It seems like if we’re going down the path of using the letter u, we might as well use it in the century coding (19uu) as well in order to be consistent. (And to maintain a consistency with MARC which the use of the letter u is suggesting to me.)
Thanks for all your work on this. This will be very helpful in our work!
Digital Collections Librarian