Lightyears

From The Encyclopaedia Expurgatia

A lightyear is the theoretical distance through which light would travel under optimal conditions, like a universe containing no matter at all, in 365.25 days at 186,283 miles per second. Which is 5,878,644,400,800 miles.

It's also 9,460,730,472,580,800 metres or nine and a half petametres.

Additionally, it's around 63,241 Astronomical Units or about three tenths of a parsec.

Within Universe 97D, a lightyear is roughly equal to a SwissYear, which is about a third of an AmericanYear, known also as a HeavyYear.