同じ時刻 and 同時: matching clock times and one shared instant
Compare nine a.m. starts on different dates with simultaneous starts in two rooms, reading the date alongside the clock time.
The same clock-time reading
同じ時刻, read おなじじこく, means the same clock time. 月曜日も火曜日も午前九時に始まりました。 says that the starts on Monday and Tuesday were both at nine a.m.
The clock readings match, but the dates differ. Two nine a.m. starts on different dates must not be merged into one instant.
Events at a shared time
同時, read どうじ, means at the same time. 二つの部屋で同時に始まりました。 says that activities began simultaneously in two rooms.
同時 supplies the time relationship. 二つの部屋で separately supplies the information about two rooms.
Read dates and time references together
同じ時刻に can also refer to events at a shared instant. Check whether the date and the time reference are the same in the actual comparison.
昨日の九時 and 今日の九時 have the same clock-time reading but belong to different dates. Read the date column too when comparing tables or records.
Did the two starts in 月曜日も火曜日も午前九時に始まりました。 occur simultaneously?
Show the answer and why
No. They occurred on different dates, Monday and Tuesday. What matched was the clock-time reading of nine a.m.