ことになっていた

was supposed to

→ こと
phrase Rare #25,519
was supposed to Used for a past plan, arrangement, or decision. Depending on context, it can also mean “was to” or “would have been the case.”
JA: 私は午後に彼と会うことになっていた。
EN: I was supposed to meet him in the afternoon.

彼は私たち食事をすることになっていた

He was supposed to have dinner with us.

彼は王位継承することになっていた

He was supposed to inherit the throne.

鈴木さんはその日の午後にスピーチをすることになっていた

Mr. Suzuki was scheduled to give a speech that afternoon.

その翌日おじ私たちを訪ねて来ることになっていた

Our uncle was scheduled to come visit us the following day.

翌朝アメリカへ出発することになっていたので、彼は興奮していた

He was excited because he was scheduled to leave for America the next morning.

私たちは翌日コンサートを開くことになっていた

We were scheduled to hold a concert the next day.

それがあれば彼の死は自殺ではなく殺人ということになっていたでしょう

If that had been available, his death would have been ruled a homicide rather than a suicide.

— きっと、うまくいく (2009)