Again the year field is ONLY for what is written on the object and you are searching for stuff that doesn't contain any 2018, 2020 or other Gregorian years, do as Peter suggested and you will get search results or use what is written on the coins.
Search with Gregorian year 2020 (LINK)
Search with Reiwa 2 (LINK)
I get over 10,000 search results with a 2018-2020 'Year' search (LINK)