I do not think that can be modified, unless if you know someone from the registrar who has access to edit that information on their database. Otherwise, that information cannot be edited in anyway. Unless, if you buy pre-expired domains, maybe a 20-year old domain that is going to expire, but not yet expire, once you have secured that domain purchase, the domain registrar will simply transfer the ownership to you, and the initial domain registration date will still be preserved - if it is 20 years, its initial registration date would still be 20 years ago, just that the domain ownership changed to you.