We're almost ready to begin public beta testing of our implementation of the MetaWeblog API for MSN Spaces. As with most technology specifications, the devil has been in the details of figuring out how common practice differs from what is in the spec.
One place where we hit on some gotchas is how dates and times are defined in the XML-RPC specification which the MetaWeblog API uses. From the spec
Scalar <value>s
<value>s can be scalars, type is indicated by nesting the value inside one of the tags listed in this table:
| Tag |
Type |
Example |
| <dateTime.iso8601> |
date/time |
19980717T14:08:55 |
The reason the above definition of a date/time type is a gotcha is that the date in the example is in the format YYYYMMDDTHH:MM:SS. Although this is a valid ISO 8601 date, most Web applications that support ISO 8601 dates usually support the subset defined in the W3C Note on Dates and Time Formats which is of the form YYYY-MM-DDTHH:MM:SS. Subtle but important difference.
Another thing that had me scratching my head was related to timezones in XML-RPC. The spec states
This just seems broken to me. What if you are a generic blog posting client like Blogjet or W.Bloggar which isn't tied to one particular server? It would seem that the only sane thing that can happen here is for the dates & times from the server to always be used and dates & times from clients be ignored since they are useless without timezones. If I get a blog post creation date of September 29th at 4:30 PM from a client, I can't use it since without a timezone I'll likely date the entry incorrectly by anything from a few hours to an entire day.
It probably would have been better to retrofit timezones into the spec than just punting on the problem as is the case now. I wonder what other interesting gotchas are lurking out there for our beta testers to find. :)