An exact time with に
Tap an imaginary clock at 七時に and say 七時に起きます. Then say 毎朝、起きます: exact point versus broad frame.
1. An exact clock point takes に
Put に directly after an exact clock time: 七時に起きます and 九時半に始まります. に marks when the action or event occurs; the verb remains at the end.
This に has the time-point function. が from lesson 26 names what is present, and へ from lesson 27 marks a destination; do not mechanically swap these particles.
毎朝、七時半に起きます。
授業は九時に始まります。
2. Broad frames without に in the neutral school sentence
毎朝, 毎日, and 毎晩 express recurrence. 今日, 明日, 昨日, 今朝, and 今晩 give a broad time frame. In this lesson's neutral target sentences, these words take no に.
A broad frame and exact point can appear together: 毎朝、七時半に起きます. Other contexts may mark time differently; this is the bounded school form, not an absolute rule for every use.
3. 何時に asks for an action time
何時ですか asks what time it is now. 何時に起きますか asks when the action occurs. The answer replaces 何時 with a clock time and keeps に: 七時に起きます.
The question and answer verbs must name the same action. 何時に寝ますか expects a bedtime, not a class starting time.
何時に寝ますか。
十一時半に寝ます。
4. Beginning and ending
In 授業は九時に始まります, 授業 is the topic, 九時に is the exact time, and 始まります says what the class itself does. 始めます, ‘start something’, is a different verb and is outside this target pattern.
終わります says an activity ends: アルバイトは午後六時に終わります. 帰ります says someone returns. Those events may happen in sequence, but are not the same.
アルバイトは午後六時に終わります。
今朝、八時に起きました。