Usage: 2 forms in 16 verses
Form Translated As     In Verse(s)
εικάδοσ twentieth LXX.Exod.12.18
twentieth day LXX.Hag.2.18
εικάδι twentieth LXX.Gen.7.11LXX.Gen.8.4LXX.Gen.8.14LXX.Num.10.11LXX.Ezra.10.9LXX.Neh.6.15
twentieth day LXX.2Kgs.25.27LXX.Esth.8.9LXX.Jer.52.31LXX.Hag.1.15LXX.Hag.2.1LXX.Hag.2.10LXX.Hag.2.20LXX.Zech.1.7

Liddell-Scott-Jones

εἰκάς (eikas) the twentieth day G:N-F

εἰκάς, άδος, ,

Aeolic dialect dative plural εἰκάδεσσι [Refs 5th c.BC+]: (εἴκοσι):—twentieth day of the month (i.e. ἡμέρα), [Refs 8th c.BC+]; πρώτη, δευτέρα, etc., μετ᾽ εἰκάδα, εἰκάδας, the 21st, 22nd, etc., [Refs 4th c.BC+], the last ten days of the month, [Refs 5th c.BC+]; τρίτῃ εἰκάδι, i.e. the 23rd, [Refs 5th c.BC+]

__II name of the sixth day of the Eleusinian mysteries (= Boedromion [Refs 5th c.BC+]
__III plural, divisions of a tribe, [Refs 5th c.AD+]