The vinalia rustica, which fell on the 19th of August, was the day the first new wine was brought into the city. This day was a holiday specifically for the growers or kitchen-gardeners (holitores), and feasts and wine drinking were the order of the day. On this occasion the "flamen dialis" offered lambs to Jupiter, and while the flesh of the victims lay on the altar, he broke with his own hands a bunch of grapes from a vine, and by this act he, as it were, opened the vintage. No "must" (young wine) was allowed to be conveyed into the city until this solemnity was performed. Although the Vinalia celebrations were originally aimed to worship Jupiter, in the later Roman Empire the festival incorporated Venus, as the goddess of the garden and wine.
AN INTERESTING SIDE NOTE: Due to the intense drinking and loss of control as a result, upper-class Roman women were supervised during this festival and sometimes given lower alcoholic content beverages.
From: A Dictionary of Greek and Roman Antiquities
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