Your conception date was around Friday 21st January, based on your Due date.
I'm due 5th October and my conception date was the 12th January according to my due date....But your due date will be based on your baby's size at the scan they took it's measurements (Usually your 12wk scan).....Just bear in mind that all baby's grow at different rates in utero, so the date you are given is not always spot on.
In my case, I know I concieved on Friday 14th, not Wednesday 12th (Hubby works away, makes it easier to narrow down)...But they were only out by two days, so it's still pretty accurate!
Hope this helps