http://www.legislation.gov.uk/id/uksi/1986/24

PART EBENEFITS

Counting of certain reckonable service in calculating amount of benefitsE30.

For the purpose of calculating the amount of any benefit—

(a)

any period which is reckonable as reckonable service by virtue of its having been reckonable under the former regulations as contributing service shall, subject to regulations E25 and E26 (part-time and non-contributing service), be counted at the same length as it would have been counted for the purpose of calculating any benefit under the former regulations, and

(b)

any reckonable service in excess of a number of complete years shall be counted as

\frac{A}{365}

of a year, where A is the number of completed days comprised in the excess.