Time + に
Grammar Pattern
at (a specific time); on (a specific day/date); in (a specific month/season/year)
Time + に
at (a specific time); on (a specific day/date); in (a specific month/season/year)
Explanation
に can mark a specific point in time when something happens.
It is used with clock times and many calendar time expressions such as days of the week, dates, and months.
However, に is often omitted with time words that are relative (like “today” or “tomorrow”) or habitual (like “every day”).
Whether に appears depends on whether the time expression is treated as a specific point or a general time frame.
Formation
Time expression + に + verb
Usage Notes
PRIMARY USE: Specific time point
Use に when the time expression is a specific point on a calendar or clock.
COMMON USES WITH に:
1) Days of the week
Use に with days like 日曜日 (on Sunday).
2) Clock time
Use に with numerical time expressions like １０時４５分 (at 10:45).
3) Months (and similar calendar points)
Use に with expressions like 九月 (in September).
DO NOT USE に (common Genki-level rule):
1) Relative time words
Examples include 今日, あした, きのう.
2) Regular intervals / habitual time phrases
Examples include 毎日, 毎晩, 毎週.
3) The question word “when”
Do not use に with いつ.
SPECIAL NOTE (style-dependent optional に):
Some broader time words can take に depending on emphasis and style.
Common examples include 朝(に) and 週末(に).