I learned that 以 can also function to mean "a certain time" or "a fixed date", for example:


However, I also know that 于 can work in the same purpose, for example:



All the example sentences are from Pleco.

I feel that in these usages, 以 is used only to express "time", and not "place". So 生以上海 is wrong.

However, if it means "a fixed date", is there any difference (and if it is what is it) between 以 and 于?

Also, is there any such prepositions that function for the same purpose?

  • see dictionaries,bkrs:于= 於 universal prep. of literary language, in, on, at; the other two have many other meanings, quoted examples may indicate low frequency usage 生于上海 :① 介词。 a>在:她生于1949年│黄河发源于青海。 b>向:问道于盲│告慰于知己│求救于人。 c>给:嫁祸于人│献身于科学事业。 d>对;对于:忠于祖国│有益于人民│形势于我们有利。 e>自;从:青出于蓝│出于自愿。 f>表示比较:大于│少于│高于│低于。 g>表示被动:见笑于大方之家。 我以三月一日返 ;以 at (a certain date or place) , 来信与十五日收到 :与:and; with; to; for;22) 介词。同,跟。 23) 介词。以。 24) 介词。替。 25) 介词。把;将。 26) 介词。被。 27) 介词。於;在。 28) 介词。向。 29) 介词。从;由。
    – user6065
    Commented Oct 27, 2017 at 17:52
  • 与 placed before verb/adjective: 与学生谈,心与柏石坚,与你没关系,与困难作斗争,其衣与花借色,请你与我对他致谢, 于 after verb:用于,出于,处于,在于,相当于,。。。
    – user6065
    Commented Oct 27, 2017 at 18:19
  • 以 bkrs 6) indicating time: 壮者, 以暇日修其孝弟 (tì) 忠信, 其弟 (dì) 以千亩之战生 ⑤ 〈书〉于;在<时间>:中华人民共和国以1949年10月1日宣告成立 ichacha: 以 [书面语] (于; 在) at (a certain time); on (a fixed date) 短语和例子
    – user6065
    Commented Oct 27, 2017 at 18:52
  • 与 is a typo, I fixed it just now.
    – Blaszard
    Commented Oct 27, 2017 at 19:19

5 Answers 5


In old saying, 以 could mean 在 or 于. For example, 余以3月1日返:I returned on March 1st.

Refer to the definition 4 in this dictionary.

However, nowadays, we don't usually use 以 for this kind of purpose any more. Instead, 于 or 在 is more common. But you could possibly hear it in those old movies. 余以3月1日返 is classic literature, and people might apply this usage of 以 when they write a classic essay, novel, and etc.


As a preposition, 以(with) and 于(at/ in) are very different.

我以三月一日返。(I take March the first come back)

It is plain wrong, the sentence make no sense.

The only way you can use 以 with a fixed date or period of time is:

  1. In a [ (A) (B)] structure -- Example: "三月一日限期" (take March the first as the deadline)

  2. use '以' as preposition 'with' -- Example: "三日时间完成这工作" (finish this job with three days time)

生于上海 (born in Shanghai) is correct

来信与十五日收到。There must be a typo. It should be "来信十五日收到" (your letter arrived at the fifteen)

can be a preposition for date or location


"生上海" (born in Shanghai) - location

"生一九一二年" (born in 1912) - date

"上午五点死亡" (died at 5:00 AM) - time

  • The example sentence is from Pleco, FYI.
    – Blaszard
    Commented Oct 27, 2017 at 18:04
  • 1
    Trust me, a living person who speak Chinese as his first language, 我以三月一日返 is grammatically incorrect; 与 in 来信与十五日收到 is a typo for 于. You can ask one hundred more people and they will all agree with me.
    – Tang Ho
    Commented Oct 27, 2017 at 18:14
  • This usage of 以 only exists in ancient texts, today it's just grammatically wrong Commented Oct 28, 2017 at 3:45
  • We shouldn't say it's grammatically wrong as of now, because you can still see the usage of 以 in 新华字典. So, it seems that it has not been obsolete completely yet.
    – dan
    Commented Oct 28, 2017 at 6:50

我以三月一日返 sounds like some Classical Chinese thing.

It is not able to compare with Modern chinese.

So you must translate it to "Chinese" first.

If you do so, this sentence will be “我于三月一日返回” or “我以三月一日为返回的期限”.

note the secound usage is “以X为Y”, not related with time.


The most widespread and traditional usages of 于/於 and are best translated as at and using, respectively. 以 was originally a picture of a person holding an object, which is an abstraction of the person using the object. The form


captures this meaning well, and translates to using X to V Y, where V is some generic verb; X could be any kind of noun, including abstract nouns like methods/ways of doing things.

于/於 is the best choice to expresses a situation at a certain date/location. While you can use 以, it is quite unnatural to do so normally unless you're trying to emphasise that the date/location is equivalent to a some generic noun. To use your example,


while grammatically correct, sounds about as awkward as

I'm returning by way of March 1st


Here is another example of using 以 as "at" : 山区的石灰岩层,以大约三十度的角度,由南向北斜. The limestone layer in the mountain area slopes from south to North at an angle of about 30 degrees

  • The example may not be quite related to the question.
    – L Parker
    Commented Aug 25, 2021 at 23:28

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