Per Jon's comment on r02f4a857bf93, do the union operation on the string ID rather than the TimeZoneInfo, to handle the possibility that the instance returned by TimeZoneInfo.Local is equivalent but not identical to one returned by TimeZoneInfo.GetSystemTimeZones().
Per Jon's comment on r02f4a857bf93, do the union operation on the string ID
rather than the TimeZoneInfo, to handle the possibility that the instance
returned by TimeZoneInfo.Local is equivalent but not identical to one returned
by TimeZoneInfo.GetSystemTimeZones().

jskeet/nodatime,zaccharles/nodatime,BenJenkinson/nodatime,BenJenkinson/nodatime,zaccharles/nodatime,zaccharles/nodatime,malcolmr/nodatime,nodatime/nodatime,nodatime/nodatime,zaccharles/nodatime,jskeet/nodatime,malcolmr/nodatime,zaccharles/nodatime,malcolmr/nodatime,malcolmr/nodatime,zaccharles/nodatime