The easiest way to find out when a home was built is to find the deed or title to the house, which typically notes the year of construction. If this information isn't listed or if the ownership documents are lost, there are other ways to look for the construction date.
In some areas, city and county deed recorder or tax assessor offices might have records related to the home's construction and ownership transfer. The first year an owner paid property taxes at the home's address, for example, may indicate when the home was built. Old newspapers may list this information as well; however, doing the research can take time, especially for homeowners who don't know exactly where to look.
Another option is to inspect original parts of the home. Pieces of concrete, for example, often indicate the year they were created. Inspecting exposed concrete in the basement may reveal the year the concrete was made, which should be close to the year the home was built. Similarly, wood is sometimes stamped with the year it was cut, so checking the attic may yield results. Pipes sometimes display the year they were made. If the home is relatively new and the original toilet is still in place, the date it was made might be stamped underneath the septic tank lid. Other household appliances sometime feature construction dates as well.