Hello,
I changed the demonetized format to "1 January 2020".
It replaces the potentially ambiguous formats "31-03-1926" (which was for the UK English and French versions) and "03-31-1926" (US English version).
Even if it may not the preferred format in some countries, it's a non-ambiguous way to express the date in full, aligned with the
catalogue guidelines.
I preferred not being consistent with banknote dates. The format "1920-Jan-01" is useful for banknotes dates because it starts with the year (hence making easy to quickly grasp a long list of dates) and because it is short, but I prefer to avoid using this order and abbreviations where it's not needed.