Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
Among the other festivals those which related to the culture of corn and wine hold the first place, while the pastoral feasts play a subordinate part. To this class belongs especially the great series of spring-festivals in April, in the course of which sacrifices were offered on the 15th to Tellus, the nourishing earth (-fordicidia-, sacrifice of the pregnant cow), on the 19th to Ceres, the goddess of germination and growth (-Cerialia-) on the 21st to Pales, the fecundating goddess of the flocks (-Parilia-), on the 23rd to Jupiter, as the protector of the vines and of the vats of the previous year's vintage which were first opened on this day (-Vinalia-), and on the 25th to the bad enemy of the crops, rust (-Robigus-: -Robigalia-).
So after the completion of the work of the fields and the fortunate ingathering of their produce double festivals were celebrated in honour of the god and goddess of inbringing and harvest, Census (from -condere-) and Ops; the first, immediately after the completion of cutting (August 21, -Consualia-; August 25, -Opiconsiva-); and the second, in the middle of winter, when the blessings of the granary are especially manifest (December 15, -Consualia-; December 19, -Opalia-); between these two latter days the thoughtfulness of the old arrangers of the festivals inserted that of seed-sowing (Saturnalia from -Saeturnus- or -Saturnus-, December 17). In like manner the festival of must or of healing (-meditrinalia-, October 11), so called because a healing virtue was attributed to the fresh must, was dedicated to Jovis as the wine-god after the completion of the vintage; the original reference of the third wine-feast (-Vinalia-, August 19) is not clear.
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Reference address : https://www.ellopos.net/elpenor/rome/1-12-religion.asp?pg=3