I need a static URL that points to the current calendar. Since there is no option to supply today's date if the argument is invalid, I can't do /calendar/month/today. Instead, the plan was to use /calendar/month/@.

It looks like arg_parts() in date_api_sql.inc was written to support this wildcard. It uses date_now() when the @-sign is used.

However, the returned array contains more key-value pairs than it would if a simple date were supplied. By hacking the returned array to eliminate the extra elements, I verified the extra array elements cause the problem. Very rough, but it works.

I do not at this point have a clean solution to recommend.