(a) The retirement system, under rules adopted by the board of trustees, shall correct an error in current service performed, or current service credit that should have been received, not more than four years before the date an application for the correction, on a form approved by the board of trustees, is received by the retirement system.
(b) The retirement system shall correct an error in prior service credit if the retirement system receives the person‘s written application for the correction not later than the fourth anniversary of the later of the date the municipality began participation in, or the person first became a member of, the retirement system.