R. Akiva says: Just as (the fruits of) threshing-floor and wine-press, which are distinct in that they grow by most water (i.e., rain, but not drawn water) are tithed according to the tithing order of the preceding year, (so, all such fruits, etc.) — to exclude greens, which, not growing by most water (but by drawn water), are tithed according to the tithing order of the year to come.
(Devarim 16:14) "And you shall rejoice": in all kinds of rejoicing.