GRAMMAR DETAIL

〜べきだった

should have

Expresses regret that an action that ought to have been taken in the past was not taken.

Examples

問題に気づいた時点で、すぐ報告するべきだった。

I should have reported it as soon as I noticed the problem.

もっと早く医者に相談するべきだった。

I should have consulted a doctor sooner.

出発前に予約を確認するべきだった。

I should have checked the reservation before leaving.

Structure: Use past べきだった instead of べきだ after a dictionary-form verb to judge what ought to have been done.
Basic usage: 出発前に予約を確認するべきだった。 expresses the retrospective judgment that the reservation should have been checked before departure.

Where the past is marked
- In 確認するべきだった, だった marks the past. Do not replace it with 確認したべきだ to form this construction.
An action that should not have been taken
- 言うべきではなかった judges saying something to have been inappropriate. Its recommendation runs in the opposite direction from retrospective 言うべきだった.