Grammar Point
particle
prt 
に

at (place, time), in, on, during

Time Expression + に

The particle に is used to mark a specific point in time when an action or event occurs. It is typically used with time expressions that contain numbers, such as specific dates, years, or clock times.

Specific Time + に

When expressing a specific numerical time, に follows the time noun directly to indicate the moment the action happens.

I wake up at seven o'clock.

I will go to Japan in August.

The party is on the tenth.

Note

に is not used with relative time expressions that do not contain numbers, such as 'today' (今日), 'tomorrow' (明日), or 'every day' (毎日). It is also generally omitted after days of the week, though it can be used optionally in formal contexts.

Words: 
に
Radicals of radicals