Consider also that there is one hour per year which does not exist and one hour per year which happens twice (at-least within the context of local time if you l

Consider also that there is one hour per year which does not exist and one hour per year which happens twice (at-least within the context of local time if you live in an area with daylight savings) There is also Namibia which used to lose hours in daylight savings time and Bangladesh which had dst in 2009 then dropped it, this makes historical time calculations tricky.