Shipping Dates For Recent Proof Sets With Varieties

It is fairly common knowledge the type 2 proof sets of 1979 and 1981 were released late in the year. What about other modern proof set varieties? When was the 1970 small date set shipped; early or late? The various no-S proof sets, when did they ship? You often see unopened boxes of proof sets on ebay and if you had an idea when the valuable varieties would have shipped you could have a clue about the potential contents by looking at the postmark on the box...