What is the difference between 于 and 以 to express "a certain time" or "a fixed date"?

Question

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

我以三月一日返。

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

生于上海

来信于十五日收到。

_{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?

Answer 1

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.

Answer 2

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 [以 (A) 为 (B)] structure -- Example: "以三月一日为限期" (take March the first as the deadline)

2. use '以' as preposition 'with' -- Example: "以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 "来信于十五日收到" (your letter arrived at the fifteen)

于 can be a preposition for date or location

Example:

"生于上海" (born in Shanghai) - location

"生于一九一二年" (born in 1912) - date

"于上午五点死亡" (died at 5:00 AM) - time

Answer 3

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.

Answer 4

The most widespread and traditional usages of 于/於 and 以 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

以XVY

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,

我以三月一日返。

while grammatically correct, sounds about as awkward as

I'm returning by way of March 1st

Answer 5

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