You are inventorying the presence of files, in this case .exe's. This table only looks at files, and therefore there is no installed date. An installed date would exist if the program were actually installed and adding information to the registry, such as at HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{GUID}\. This information is gathered by software inventory and entered into the Inv_AddRemoveProgram table as InstallDate.
You could add ifd.[ModifiedTime], to your SELECT statement, but this is the only time/date information included in Inv_Installed_File_Details.