`date` and timestamp format

[Super Pik Master]

Hello

I've been trying to print a timestamp format (I mean seconds from 1 Jan 
1970) with `date` program from coreutils package.
There is an option -d but it does not take the numerical timestamp as an 
input.

Is there a chance to enhance the functionality by allowing the above? Or 
add an option like -t to read timestamp and then print it in one of 
allowed formats. It would be very convenient.

I tried to hack the sources myself, but it seems, I am not skilled 
enough to change the code and keep it consistent and working. So here 
comes my mail.

Thanks.
--
Pik Master