Short answers, pulled from the story.
Stativae were annual holidays with fixed dates that never changed. Conceptivae acted as moveable feasts announced by magistrates or priests. Imperativae were held on demand for special celebrations or expiations.
January began marking the entry of consuls into office from 153 BC onward. Festivals during this time included those for Aesculapius and Vediovis. The month also featured Parentalia running from the 13th to the 22nd.
Romans instituted a nine-day public festival following reports of stones falling from the sky on Mons Albanus. This event occurred after Livy reported the Roman destruction of Alba Longa in the 7th century BC. The celebration served as an expiation for displeasure shown by the Alban gods.
Cicero stated that Numa Pompilius established markets to facilitate trade when people gathered for religious festivals. These fairs evolved from wholesale trade to specialized retail events like the Sigillaria attached to Saturnalia. Surviving inscriptions record specific dates including July 14 through 19 and September 20 through 23.
Varro defined feriae as days where public business was suspended and slaves received rest. Cicero said free citizens should not engage in lawsuits or quarrels during these periods. Those who worked inadvertently could pay a fine or offer up a piaculum usually a pig.