x1 is a season/is seasonal [cyclical interval], defined by interval/property x2, of year(s) x3.
Also anniversary (= citsydei, na'arcitsydei), jubilee (= mumnoncitsi); the period of time may be short or long as indicated by x2, and may occur every year or every nth year as indicated by x3 (default every year); (x2 and/or x3 may need metaphorical restriction: djecitsi, pavdeicitsi; also equinox, solstice, time of year. See also cedra, crisa, critu, dunra, ranji, temci, vensa, jbena.