だてじゃありませんでした
伊達じゃありませんでした
datejārimasendeshita

Noun
Desu Copula
na-Adjective

The polite, past negative form of だて

1. It wasn't as it seemed.; It wasn't simple.; It wasn't ordinary.

Past/Perfective
Negative
Polite
Terminal Form
Usually Written in Kana