The difference between "since" and "from"

ViceidolI have known her since 1994. (correct)

Can it be rephrased as " I knew her from 1994." ? No, this sentence is incorrect. It could be rephrased as: I have known her for thirteen years.

From the moment he saw her, he lo

Use "since" when you're indicating the beginning of the time period (it refers to the starting point):
I have known her since 1990.
We haven't seen them since June.
She has been there since eight o'clock.

Use "for" when you're talking about a period of time (up to the present):
I have known her for 17 years.
We haven't seen them for

I really thank both of you!!

this is helpful..

the person is not answering the call then i want to mail the guy.

should i mention that

i have been calling you from 15 days
or i'm calling you from past 15 days

answer me which is correct and suggest me the best way i can mail the person.

I have been calling you for 15 days, since the 1st day you aren't picking my call.

That's not good English.
Say eg I have been calling you for 15days, but you haven/t returned any of my calls.
Clive

I have been calling you from 15 days, but you haven't received any of my calls.
Is this right english...?

'From' is not correct. Say 'for'.

you haven't received any of my calls. Sounds like the person's phone was broken.
you haven't returned any of my calls. The person knew you called, but never called you back.

Clive