dir-spec.txt says ``` "HSDir" -- A router is a v2 hidden service directory if it stores and serves v2 hidden service descriptors and the authority managed to connect to it successfully within the last 24 hours. ``` That sure makes it sound like "was found reachable at least once in the past day". The actual test is in dirserv_thinks_router_is_hs_dir(): if it's Running now, and its uptime appears to be >= 25 hours.