にPer-period frequency or duration
After a period, に sets that period as the unit for saying how often something happens or how much time is spent on it.
The period is a measuring unit
Read the phrase before に as the recurring unit: each day, each week, each month, and so on. The count or duration that follows tells you what happens within each unit.
Counts and durations
A recurring unit versus one event time
In the per-period pattern, the phrase before に is a recurring unit and is followed by a count or duration. Time-point に, by contrast, identifies when one event occurs.
More examples
月に一回、祖母に電話します。
I call my grandmother once a month.
Analyze一年に二回、歯科検診を受けます。
I have a dental checkup twice a year.
Analyze一日に三十分、声に出して読みます。
I read aloud for thirty minutes a day.
Analyze週に四日、家で仕事をします。
I work at home four days a week.
Analyze一週間に一時間、庭の手入れをします。
I spend one hour a week tending the garden.
Analyze一か月に二冊、小説を読みます。
I read two novels a month.
Analyzeこのバスは一時間に三本来ます。
This bus comes three times an hour.
Analyze