You can work out roughly the date of conception. But that doesn't ness mean that is the day you had sex. Sperm can live inside you for up to a week. Usually takes around 2/3 days between.
Yes there are charts on internet look them up
i think its quite hard to pinpoint the exact day because you can never really be sure when you ovulate or if you ovulate on time or a little late, the only way you could be a100% sure would be to of had IVF, life would be so much easier if wecould pinpoint the exact day