The Brazillian "Dia dos Namorados" is celebrated on june 12th. But, that is only in Brazil. In Other parts of western world the traditional date is February 14th, St Valentine's day or just Valentine's Day.
Its origin is in the pagan parties of Lupercalia in Old Rome, Which happened in the middle of February
The feasts werw to honor the God Lupercus so that no harm would come to the flocks and shepherds and the goddess of love juno Februata. In these festivals, the young women would write their names in pieces of paper or cloth and place them in a jar. The young boys would draw a name and the boys and girls who were matched would be considered partness for the year. wich began in march
There were two reasons for the change of the date in Brazil: to boost sales in June and to take advantage of the proximity of June 13th, Saint anthony's day (Saint Anthony is the patron saint of weddings)
The success was not immediate. Only after many years did this date become sysnonysmous with romance in Brazil. However, unlike the Brazilian version of Valentine's day, it is the costom for people in European countries to give presents not only to their sweerhearts but also to the ones they loke most, such as their parents, brothers , sisters or friends