Learners of Japanese often wonder when to use the particle に with time expressions.
月曜日に学校へ行きます。
Getsuyōbi ni gakkō e ikimasu.
(I go to school on Monday.)
This is correct.
But 毎日に学校へ行きます is unnatural.
Mainichi ni gakkō e ikimasu.
(I go to school every day.)
Why is there such a difference? This article explains which time expressions normally take に, which do not, and which are optional.
Time expressions that do not take に
Relative time words like 今日, 明日, 昨日 already point to a time relative to “now,” so に is not used.
Examples:
私は今日図書館へ行きます。
Watashi wa kyō toshokan e ikimasu.
(I will go to the library today.)
明日友だちに会います。
Ashita tomodachi ni aimasu.
(I will meet a friend tomorrow.
Habitual expressions like 毎日, 毎朝, 毎週 also do not take に, because they describe repeated frequency, not a single point.
Examples:
私は毎朝ジョギングをします。
Watashi wa maiasa jogingu o shimasu.
(I jog every morning.)
Other words that do not take に
今日 kyō (today) 明日 ashita (tomorrow) 昨日 kinō (yesterday)
今 ima (now) さっき sakki (just now)
今朝 kesa (this morning) 今晩 konban (tonight)
先週 senshū (last week) 来週 raishū (next week) 今週 konshū (this week)
去年 kyonen (last year) 来年 rainen (next year) 今年 kotoshi (this year)
一昨日 ototoi (the day before yesterday) 明後日 asatte (the day after tomorrow)
毎日 mainichi (every day) 毎朝 maiasa (every morning) 毎晩 maiban (every evening)
毎週 maishū (every week) 毎月 maitsuki (every month) 毎年 maitoshi (every year)
Expressions that normally take に
These are time expressions that refer to a specific, fixed point in time. If you can mark it on a calendar or clock, you normally need に.
Examples:
2025年に卒業しました。
Nisen nijūgo nen ni sotsugyō shimashita.
(I graduated in 2025.)
9月に旅行します。
Kugatsu ni ryokō shimasu.
(I will travel in September.)
11日に試験があります。
Jūichi nichi ni shiken ga arimasu.
(There is an exam on the 11th.)
月曜日に会議があります。
Getsuyōbi ni kaigi ga arimasu.
(There is a meeting on Monday.)
3時半に集合します。
Sanji han ni shūgō shimasu.
(We will meet at 3:30.)
クリスマスにパーティーをします。
Kurisumasu ni pātī o shimasu.
(We will have a party on Christmas.)
When combining with frequency words, the に attaches to the final element.
Examples:
毎週月曜日にミーティングがあります。
Maishū getsuyōbi ni mītingu ga arimasu.
(There is a meeting every Monday.)
来年の3月に旅行します。
Rainen no sangatsu ni ryokō shimasu.
(I will travel in March next year.)
Optional に
Some expressions can appear with or without に.
The general rule is: use に when you are talking about a specific one-time event, and omit に when you are describing a habit or routine.
However, in many everyday cases, both forms are possible and the meaning is almost the same. Adding に makes the time more explicit or formal, while leaving it out sounds more casual in spoken Japanese.
午後に電話します。
Gogo ni denwa shimasu.
(I will call in the afternoon. In casual speech, 午後電話します is also common. Both are natural, but with に it feels a bit clearer or more formal.)
Examples:
朝散歩します。
Asa sanpo shimasu.
(I take a walk in the morning — habit.)
朝に地震がありました。
Asa ni jishin ga arimashita.
(There was an earthquake in the morning — one-time event.)
午前中に行きます。
Gozenchū ni ikimasu.
(I will visit sometime during the morning — emphasizes “within that period.”)
The role of は
Time words usually act like adverbs, so は is not normally added. But it can appear for contrast or emphasis.
Examples:
コーヒーは毎日は飲みません。
Kōhī wa mainichi wa nomimasen.
(As for coffee, I do not drink it every day.)
今日は雨ですが、明日は晴れるでしょう。
Kyō wa ame desu ga, ashita wa hareru deshō.
(Today it is rainy, but tomorrow will be sunny.)
Special cases
Frequency plus period always requires に, because it means “per.”
Examples:
月に三回
Tsuki ni sankai
(Three times per month)
一日に一回
Ichinichi ni ikkai
(Once per day)
Relative time plus の plus a noun can take に.
Examples:
明日の会議に出ます。
Ashita no kaigi ni demasu.
(I will attend tomorrow’s meeting.)
去年の夏に旅行しました。
Kyonen no natsu ni ryokō shimashita.
(I traveled last summer.)
Final Thoughts
Relative time words like 今日 and 明日 and frequency words like 毎日 and 毎週 do not take に.
Calendar-based points like years, months, dates, days of the week, times, and holidays normally take に.
Expressions like 朝, 午後, or 冬 may or may not take に, depending on whether you describe a repeated habit or a one-time event. In many cases, both are possible, with に sounding clearer or more formal, and omission sounding casual.
The particle は is not usually added, but it can appear for contrast or emphasis.
The key is simple: if the word refers to a single, specific point, use に. If it describes a habit or frequency, do not.