Grammar check

[babyblue]

Hi, I have a sentence to ask you about.

"We have known for 3 years by April".

If the "April" means one point of time in the past like last April, does this sentence sound nice and make sense?

[Narayanan Krishnaswamy]

‘By April’ means before April.
When can you complete?
By nine pm.That means the work can be completed before the time mentioned.
In narration it is possible to use this as you mentioned.

‘By April 1982, his attitude changed.’

Your expression lacks clarity.
In normal conversation it is better to avoid this and use a different construction.