I disagree. "Pro-forma" is quite recent as a common way to report earnings. In the past it was reserved for unusual situations like mergers or highly unusual charges or gains against earnings. Now it is used every quarter for most every company and the "one time charges" are a complete joke that recur every quarter and exclude even a lot of common operating expenses. The now common practice of charging off inventory (an excluded "one time charge") one quarter then selling it the next quarter using a zero cost basis (100% profit margin) is both very new and getting very common among tech companies. It is also a fraud against the stockholders, in my opinion.
No, historical comparisons are only valid if you use GAAP earnings.