間違ってました

was wrong, was mistaken

→ 間違う

間違っ make a mistake, be wrong + て Te-form (conjunctive form) + まし Polite + た Past tense

verb · informal, past tense Rare #42,145

was wrong, was mistaken Conversational contraction of 間違っていました.

JA: さっきの説明は間違ってました。

EN: My earlier explanation was wrong.

Conjugation of 間違う

Indicative past

I was wrong…

— तुम्बाड (2018)

Was I wrong?

— 新感染ファイナル・エクスプレス (2016)

I was wrong.

We were wrong.