Does the discoverability rule apply to the starting date of the limitation period?

As stated by Borins J. in Aguonie v. Galion Solid Waste Materials Inc., supra, in considering the application of the discoverability rule to the starting date of the limitation period, at p. 172: It is a question of fact when the cause of action arose and when the limitation period commenced. The application of the discoverability rule is premised on the finding of these facts: when the appellants learned they had a cause of action against the respondents; or, when, through the exercise of reasonable diligence, they ought to have learned they had a cause of action against the respondents.