Dewiswyd y dyddiad i gydnabod y gwenynwr o Slofenia, Anton Janša. Cafodd ei eni ar 20 Mai 1734 yn Carniola (Slofeniad erbyn hyn) ac mae’n cael ei gydnabod fel tad gwenyna.
The date was chosen in recognition of Slovenian apiarist, Anton Janša. He is acknowledged as the pioneer of beekeeping and was born in Carniola (now Slovenia) on May 20th, 1734.