+However, the leap second support of this package is rarely used directly
+because POSIX requires leap seconds to be ignored
For what it's worth, I never like the term "ignored" in this context. For example, I might claim that POSIX requires leap seconds to be taken into account (in order to remove them from the "seconds-since-the-epoch" count), and that it is the "right" clock that ignores them. Conversely, others might say leap seconds are ignored in the POSIX absolute<->civil conversions, and taken into account in the "right" conversions. So, "ignored" doesn't really apply to either system ... they both deal with leap seconds in some fashion.