Hi,
A short answer is that it's your notebook, so write it however you wish. I'd write 8/Feb/2006.
How you write dates that other people will read and understand is an interesting question. Briefly, if you write in numbers, it can often be unclear whether you are writing day/month or month/day, eg 8//3/06. So, write in a way that makes it clear, eg 8/Feb/06 or 8/31/06.
Best wishes, Clive