When loading ‚UTC‘ the function tzload seems to use an uninitialized value here: localtime.c:574: for (i = 0; i < sp->typecnt; ++i) if (sp->types[i] == 0) // <- sp->types[0] is uninitialized (sp->typecnt is 1) break; It might be a user error on my side. But I am unable to spot it. Note that the UTC file was generated with an older version. This is with tzcode2014g - Jörg