に

About

The に particle can be used with time nouns to mark them as the "target" time for an event or action.

E.g. ５時じに行いきます。
"I'll go at 5."

Where 5 is the target time of the action 行いく

に can only mark specific time nouns, such as a time on the clock, a day of the week, a season, or a holiday. に cannot mark ambiguous times, or those that can't be expressed numerically such as 今いま ("now"), or 最近さいきん ("recently").

Summary

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  に can be used to mark the time an action takes place

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  に can only be used in combination with specific times