The Tite prose documentation says, in section 4.1, "use date with when value (formatted yyyy-mm-dd) to record date information". However, for cases where the date does not include a day of the month (like "October 1999"), the way to encode this in regular TEI would be to follow the W3C date format and use <date when="1999-10">, not <date when="1999-10-00"> or something else involving an invented day of the month. I recommend clarifying this in the Tite prose since it seems that this isn't too complicated an instruction for a keyboarder.
Will return to this once tickets 3136934, 3136935 3136936, and 3164403 are
resolved, bringing canonical and Apex versions of Tite into alignment.
Clarifying the prose seems straightforward; Marking as GREEN.
Reconciliation of Apex Tite and canonical Tite now complete, so we can proceed with implementation.
Implemented at revision 13080.