There are two parts to this.
The source attributes. The only date-type attribute in Tinderbox is a Date-time field. as the underlying value is a millisecond offset from the Unix epoch, there is no fuzzy setting per se. I generally use the first of the month is wanting a generic date and a specific time too (e.g. “12:00”) so it’s a reminder to myself that this is likely a fuzzy date even if the data makes it appear otherwise.
Querying. A dat-ime attribute can be queried discretely for its month (and year, day, etc…) so you could, for instance ask for
$StartDate.month==11 to find a fuzzy month of November. See date.month().
So even if you need to set a notional day & month (indeed time too) you can still query on a moth or year (or both). So you might see “1/12/1773 12:52” (or “12/1/1773 12:52” in in the US) as a Date-type attribute value but you can still query for
$DateAttribute.year==1773 & $DateAttribute.month==12 and get matches to all notes where the attribute $DateAttribute has a fuzzy date of December 1773.