〜予定
plan, schedule, is due to
Verb dictionary form / Noun の + 予定 (です)
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予定 means "plan" or "schedule", and after a verb it says something is scheduled: 来週、京都へ行く予定です, "I'm due to go to Kyoto next week".
Compare つもり, which is your intention. 予定 sounds more fixed and less personal: it's in the diary. That makes it the natural word for timetables and arrangements: 会議は三時に始まる予定です, "the meeting is due to start at three".
As a noun it's everyday: 明日の予定は?, "what are your plans for tomorrow?"; 週末は予定がありません, "I've got nothing on at the weekend".
予定でした is "was supposed to", usually when things changed: 十時に着く予定でしたが、遅れました.
Examples
来週、京都へ行く予定です。
I'm due to go to Kyoto next week.
会議は三時に始まる予定です。
The meeting is due to start at three.
明日の予定は何ですか。
What are your plans for tomorrow?
電車は十時に着く予定でしたが、遅れました。
The train was due at ten, but it was late.
週末は特に予定がありません。
I've got nothing planned for the weekend.