So I've been researching nominative vs. genitive Latin.

dominus (nominative)
domini (genitive)

The correct translation of "In the year of our Lord" is "anno domini" (another thing to note, the Romans didn't use capitals or lowercase, or more correctly, everything was written in what we consider capitals. They didn't use spaces between words, either).

"Dominus" is how a slave would address the male head of the household. "Domina" is how a slave would address the female head of the household.

So "domnia" would be the nominative form. As far as I can tell "dominae" is the genitive.

So the correct Latin (I think) for "In the year of our Mistress/Lady" would be "anno dominae".

I'm not sure how that is pronounced as compared to "domina".

-Chris