Finally managed to build a binary clock like this one : http://bp2.blogger.com/__HLRN4QOAxg/R3r6_XJt0dI/AAAAAAAAAE8/b9jjVMmCmCQ/s1600-h/binaryclock.JPG, which I found here : http://projectpotpourri.blogspot.com/2008/01/your-favorite-geek-desk-toy-sucks.html
It works really well and keeps time as accurately as the arduino clock will allow, which so far seems to be pretty accurate ! The clock has an hours, minute and seconds row and to read the clock you have to know that :
top LED = 32 (except for in hours column where top LED is the 2nd one described here ) 2nd = 16 3rd = 8 4th = 4 5th = 2 6th = 1
than you just add up the numbers of the LED's lit and you get the value of that row.
If you have followed the link and are finding the image hard to understand then it is :
negative (short) leg of hours LED column go to digital pin 12 via a 320 ohm resistor, although I used a 240 ohm one. It is the same for the minutes (go to pin 11) and seconds to pin 10.
the top LED of each column goes to pin 9 (except for the top hours LED), second ones down (top hour LED) go to pin 8, 3rd led's go to pin 7 and so on counting down in pins until you reach the last LED's.
code is on the website, to enter current time just change the "int hours, int minutes and int seconds" values near the top of the code.
thanks to the owner of the website who ever you are !