δυνδεκάτῃ
From LSJ
Frisk Etymological English
Grammatical information: numeral
Meaning: ἡμέρᾳ δωδεκάτῃ H.
Origin: XX [etym. unknown]
Etymology: After ἑνδέκατος acc. to Schulze Q. 178., which gives no explanation. Latte follows Voss and reads δυοδεκάτῃ, against the alphabet. Could not it be simply *δωδεκάτῃ?