Create Sandbox for Account Established Date (Customer Account Level)

Summary

Currently, when creating a new customer account, the default date is set to System Date in the Account Established Date field but I need it to be a date in the past i.e. 01-Jan-2000

Content (required):

Currently, when creating a new customer account, the default date is set to System Date in the Account Established Date field but I need it to be a date in the past i.e. 01-Jan-2000. Does anyone know if this can be achieved via a Sandbox? I attempted to create a Sandbox for the requirement but I have been unsuccessfully so far. Any ideas? My understanding is there is no standard functionality available such as a Profile Option to set the date.