<p>Both of the "天" and "日" as the "量词" are correct.</p>

<p>In the modern standard Chinese, people will say "我觉得我会待两三天" in their daily life, and will say "我预计我将停留两三日" in the formal situation such as applications or official documents.</p>

CC BY-SA 3.0
2016-08-31T08:04:07.607Z
2016-08-31T08:04:07.607Z
Swain
<p><strong>Basic difference:</strong></p>

<p>天 (n) sky; day</p>

<p>日 (n) sun ; day; date</p>

<blockquote>
  <p>When stating number of days, you can use either 日 or 天</p>
</blockquote>

<p>Example:</p>

<p>三個月另八日 /三個月另八天 ( three months and eight days)</p>

<p>十六日 / 十六天 ( 16 days) </p>

<blockquote>
  <p>For non-specific day, you can use either 日 or 天  </p>
</blockquote>

<p>Example:</p>

<p>今日，昨日，明日= 今天，昨天，明天 (today, yesterday, tomorrow)</p>

<p>這一日 = 這一天 (this day)</p>

<p>那一日 = 那一天 (that day)</p>

<p><em>today, yesterday, tomorrow, this day and that day can be any day on calendar.</em></p>

<blockquote>
  <p>When stating a date on calendar, use 日 or 號</p>
</blockquote>

<p>Example:  </p>

<p>三月八日 / 三月八號 ( 8th March) </p>

<p><em>you cannot say 三月八天</em></p>

<blockquote>
  <p>When stating a specific date, use 日</p>
</blockquote>

<p>Example:  </p>

<p>國慶日, 開放日 ( Independent day, open day) </p>

<p><em>you cannot say 家長天, 開放天</em></p>

<p><strong>In summary:</strong></p>

<ul>
<li>When stating number of days, 天 and 日 are interchangeable </li>
<li>For non-specific date, 天 and 日 are also interchangeable</li>
<li>When stating specific date, use 日 </li>
</ul>

<blockquote>
  <p><em>but I'm not sure which to use in phrases such as "I've been in Taiwan for 25 days".</em></p>
</blockquote>

<p>Since you are referring to the number of days, you can use <strong>either.</strong></p>

CC BY-SA 3.0
2016-08-31T09:43:07.280Z
2016-08-31T10:29:28.307Z
2016-08-31T10:29:28.307Z
Tang Ho
<p>For daily usage I suggest you use "天", but "日" is still widely used in literacy (especially old books) and on formal occasions.<br>
For example:<br>
扬州十日 (A )Ten Day('s massacre) in Yangzhou<br>
我觉得我会呆两三天。 I think I will stay two or three days.  </p>

<p><strong>EDIT:</strong> More examples for you:<br>
过年七天乐(a popular TV program) 7 Days' Fun on New Year<br>
北京一日游 a one-day tour in Beijing<br>
And you may always say 天 in daily use instead of 日:<br>
给我十天时间就够了。 Ten days are enough for me.<br>
本航班需要航行一天又六个小时。 This flight will take one day and six hours.<br>
Plus, for Sunday, 星期天 is used in spoken and informal languages, while 星期日 in formal:<br>
星期天一起出去玩好吗？ Shall we go out on Sunday?<br>
截止日期为星期日晚九点。 The deadline is 9 p.m, Sunday.  </p>

<p><strong>EDIT:</strong> For your example, the correct word is "天".<br>
我已经在台湾呆了25天。I've been in Taiwan for 25 days. </p>

CC BY-SA 3.0
2016-08-31T16:10:18.030Z
For Sunday, 周日 is common and not that formal, while 周天 is extremely rare and could be misunderstood
jf328
CC BY-SA 3.0
2016-08-31T07:56:44.187Z
2017-06-14T07:07:44.883Z
2017-06-14T07:07:44.883Z
Winfred Huang
<p>You should use "天" here, since it needs "量词(unit)" here. </p>

<p>Both 日 and 天 could be used as noun like "day" in English. e.g. 星期天／星期日 are both correct for "Sunday". But you should always use 天 when you try to express "a number of days"， like 十天，三天，etc. </p>

<blockquote>
  <p>I think I will stay two or three days.
  我觉得我会待两三天。</p>
</blockquote>

<p>But there are exceptions as well. When you want to use a phrase which contains days, usually you should use 日 but not  天。
e.g </p>

<blockquote>
  <p>我们报了一个新马泰七日团。
  We ordered a Singapore-Malaysia-Thailand seven-days group tour. </p>
</blockquote>

CC BY-SA 3.0
2016-08-31T07:55:29.347Z
So 天 acts as counter/classifier in such sentences? I don't need any other word to be counter/classifier? Adding in 个 would be wrong?
hippietrail
CC BY-SA 3.0
2016-08-31T07:59:36.433Z
You don't need. Just say “number ＋天”。
thinwa
CC BY-SA 3.0
2016-08-31T07:50:39.113Z
2016-08-31T08:04:48.890Z
2016-08-31T08:04:48.890Z
thinwa
<p>I know of the words 日 and 天, which both mean "day" in Chinese, but I'm not sure which to use in phrases such as "I've been in Taiwan for 25 days".</p>

<p>When I look in Wiktionary I'm even more confused:</p>

<ul>
<li>日 is marked "literary or dialectal"</li>
<li>天 is marked "Obsolete sense in Modern Standard Chinese - may be preserved in fossilised compounds and expressions or other varieties of Chinese."</li>
</ul>

<p>So which should I use for saying things like "I think I will stay two or three days"?</p>

<p>Maybe there's a third word I don't know about?</p>

CC BY-SA 3.0
2016-08-31T08:18:43.330Z
why not feed ＂days＂ to jukuu： １２。母牛的发情周期平均为21天。２３。 这几天你显得很轻松。２５。总之，这两天我们玩得非常好。etc。

better, good old days日子: ２２。我们期待较好的日子的来临。  ２７。成年人常常回想过去的日子。
or Line Dict／examples： 5天的宽限。3天后开赛。交货期为28天。 etc。
user6065
CC BY-SA 3.0
2016-08-31T21:21:09.390Z
It means that you shouldn't rely on Wiktionary. 天 is in no way obsolete as a word for counting days.
米好 '-'
CC BY-SA 3.0
2016-09-01T04:05:56.470Z
@michau: Indeed. I use Wiktionary almost daily since 2002, but I *never* rely on it (-:
hippietrail
CC BY-SA 3.0
2017-06-14T16:39:19.110Z
You may use 日 in 三日票, 七日游 only, in this case you can see that 三日 and 七日 likes an adjective for the noun 票 and 游. You may use 三天 or 三日 to express three days, but the 三天 is commonly used. You can use both 2月15日 or 2月15号 to express February, 15th.
xenophōn
<word-choice><synonyms><time>
Which word to use for "day" when talking about lengths of time?
# Which word to use for "day" when talking about lengths of time?

(Asked by: username_0 on 2016-08-31)

I know of the words 日 and 天, which both mean "day" in Chinese, but I'm not sure which to use in phrases such as "I've been in Taiwan for 25 days".

When I look in Wiktionary I'm even more confused:

* 日 is marked "literary or dialectal"
* 天 is marked "Obsolete sense in Modern Standard Chinese - may be preserved in fossilised compounds and expressions or other varieties of Chinese."

So which should I use for saying things like "I think I will stay two or three days"?

Maybe there's a third word I don't know about?

**Tags:** word-choice, synonyms, time

> **Comments:**
> **username_1**: why not feed ＂days＂ to jukuu： １２。母牛的发情周期平均为21天。２３。 这几天你显得很轻松。２５。总之，这两天我们玩得非常好。etc。  better, good old days日子: ２２。我们期待较好的日子的来临。  ２７。成年人常常回想过去的日子。 or Line Dict／examples： 5天的宽限。3天后开赛。交货期为28天。 etc。  
> **username_2**: It means that you shouldn't rely on Wiktionary. 天 is in no way obsolete as a word for counting days.  
> **username_0**: @michau: Indeed. I use Wiktionary almost daily since 2002, but I *never* rely on it (-:  
> **username_3**: You may use 日 in 三日票, 七日游 only, in this case you can see that 三日 and 七日 likes an adjective for the noun 票 and 游. You may use 三天 or 三日 to express three days, but the 三天 is commonly used. You can use both 2月15日 or 2月15号 to express February, 15th.  

---

## 4 answers

### Answer by username_4 on 2016-08-31. Score: 4

Both of the "天" and "日" as the "量词" are correct.

In the modern standard Chinese, people will say "我觉得我会待两三天" in their daily life, and will say "我预计我将停留两三日" in the formal situation such as applications or official documents.


---

### Answer by username_5 on 2016-08-31. Score: 4

**Basic difference:**

天 (n) sky; day

日 (n) sun ; day; date

> When stating number of days, you can use either 日 or 天

Example:

三個月另八日 /三個月另八天 ( three months and eight days)

十六日 / 十六天 ( 16 days)

> For non-specific day, you can use either 日 or 天

Example:

今日，昨日，明日= 今天，昨天，明天 (today, yesterday, tomorrow)

這一日 = 這一天 (this day)

那一日 = 那一天 (that day)

*today, yesterday, tomorrow, this day and that day can be any day on calendar.*

> When stating a date on calendar, use 日 or 號

Example:

三月八日 / 三月八號 ( 8th March)

*you cannot say 三月八天*

> When stating a specific date, use 日

Example:

國慶日, 開放日 ( Independent day, open day)

*you cannot say 家長天, 開放天*

**In summary:**

* When stating number of days, 天 and 日 are interchangeable
* For non-specific date, 天 and 日 are also interchangeable
* When stating specific date, use 日

> *but I'm not sure which to use in phrases such as "I've been in Taiwan for 25 days".*

Since you are referring to the number of days, you can use **either.**


---

### Answer by username_6 on 2016-08-31. Score: 2

For daily usage I suggest you use "天", but "日" is still widely used in literacy (especially old books) and on formal occasions.  
For example:  
扬州十日 (A )Ten Day('s massacre) in Yangzhou  
我觉得我会呆两三天。 I think I will stay two or three days.

**EDIT:** More examples for you:  
过年七天乐(a popular TV program) 7 Days' Fun on New Year  
北京一日游 a one-day tour in Beijing  
And you may always say 天 in daily use instead of 日:  
给我十天时间就够了。 Ten days are enough for me.  
本航班需要航行一天又六个小时。 This flight will take one day and six hours.  
Plus, for Sunday, 星期天 is used in spoken and informal languages, while 星期日 in formal:  
星期天一起出去玩好吗？ Shall we go out on Sunday?  
截止日期为星期日晚九点。 The deadline is 9 p.m, Sunday.

**EDIT:** For your example, the correct word is "天".  
我已经在台湾呆了25天。I've been in Taiwan for 25 days.

> **Comments:**
> **username_7**: For Sunday, 周日 is common and not that formal, while 周天 is extremely rare and could be misunderstood  

---

### Answer by username_8 on 2016-08-31. Score: 1

You should use "天" here, since it needs "量词(unit)" here.

Both 日 and 天 could be used as noun like "day" in English. e.g. 星期天／星期日 are both correct for "Sunday". But you should always use 天 when you try to express "a number of days"， like 十天，三天，etc.

> I think I will stay two or three days.
> 我觉得我会待两三天。

But there are exceptions as well. When you want to use a phrase which contains days, usually you should use 日 but not 天。
e.g

> 我们报了一个新马泰七日团。
> We ordered a Singapore-Malaysia-Thailand seven-days group tour.

> **Comments:**
> **username_0**: So 天 acts as counter/classifier in such sentences? I don't need any other word to be counter/classifier? Adding in 个 would be wrong?  
> **username_8**: You don't need. Just say “number ＋天”。  

---

