My mother swears up & down that my MG sister could tell time perfectly before she was 2, but who knows. DD4 is still mostly uninterested, though she's been reading a digital clock for years. But we don't have an analog clock or a calendar.
As for testing, I think mainly people test before 6 only if they have some specific need for it (e.g., school entrance or suspected disability). Tests before 6 are generally not as reliable. I don't think testing before then is necessary in most cases, and we definitely don't plan to test before 6 (unless we get some sort of testing scholarship, LOL). I think the WISC will better capture DD's abilities than the WPPSI.
