GIPS question on 5 years performance record business, question, standards, represent

Zesty

Say a firm has been in business for over 10 years and they decide they want to start being GIPS compliant. The standards say they must present 5 years of GIPS peformance as they are a firm that's been around 5 or more years. If the last 5 years they were non-compliant, do they then have to redo and represent all their preformance data from the last 5 years?

It seems near impossible to recalculate their previous 5 years to GIPs. Redoing cost vs market, trade date vs settlement date, etc.

Am I missing anything here?