Like I said, within the context of UTC, leap seconds should not be accounted for. UTC is an arbitrary time system and can have both static rules, like leap years, and dynamic rules, like leap seconds. Every conforming UTC system should operate like the leap second never occurred. All interval calculations will remain correct under those conditions.
Such a time system should not be used for "real" time sensitive systems like celestial mechanics, crypto certificates, or medical devices. There are better time systems for that. Accordingly, mapping between UTC and some other system will not necessarily yield a one-to-one mapping.