Dan. [ei], [ui] became [ī], [ū] in Primitive Danian; [ei|ui] > [ī|ū]

Dan. [ei], [ui] became [ī], [ū] in Primitive Danian; [ei|ui] > [ī|ū]
In Primitive Danian, the diphthongs [ei] and [ui] simplified to long vowels [ī] and [ū] (PE19/25-6). A similar change of [ei] > [ī] occurred in Proto-Germanic (ref/@@@).

Reference ✧ PE19/26

Phonetic Rule Elements

[ei] > [ī] ✧ PE19/25 (ei > †ī)
[ui] > [ū] ✧ PE19/25 (ui > †ū)