<p>In retroconversion, the values given to the element and its
attributes should reflect the conventions of the particular
catalogue as expressed in the catalogue or, if necessary, as
inferred by the encoder. (If inferred, a note to this effect may
be added in <gi>encodingDesc</gi>.)</p>
<p>
The consolidated guidelines recommend:
We could encode this: https://syriaca.org/documentation/dates.html