One of the land before time books I have claims the time span between Littlefoot's hatching and the next scene in the land before time (when he asks his mother if there isn't anything more to eat) to be five years. I suppose this was just a guess of the author though. It is very difficult to estimate the age of the characters. On the one hand we get glimpses at some characters (Dinah, Dana, Tricia, Tippy) which strongly suggest that they all went through a period of "hatchlinghood". We never saw this period for Spike though who didn't live through whatever time may have elapsed between Littlefoot's hatching and his first talking in the original movie. Spike's size tripled (or more) in the first moments after he hatched. Perhaps his inability to talk was the only real indication for his being much younger than the others in the original movie and perhaps that inability to talk was not originally meant to be an indication for anything but his younger age. Anyway.
Most of the land before time movies action could be squeezed in a time span of just a few days. Exceptions are LBT 3 (realistically it would take several years at least for the Great Valley to regrow to its original splendor after the fire), LBT 5 (it would not take as long for the Valley to regrow without being burned down, but still it would take a while, and LBT 8 (passing of one cold time).
I strongly suppose Littlefoot and the others to be still rather young (ten years perhaps). Even Hyp, and his palls who are probably supposed to be teenagers come accross as rather young teenagers. There are cases when Littlefoot and the others show signs of thinking very much in child terms (maybe the Thundering Falls are tired and need to rest) though perhaps some of their thinking may be dinosaur thinking rather than child thinking (I suppose the grownup dinosaurs too might have a hard time trying to figure out the origin of an echo).
