The Feast of the Immaculate Heart of Mary is celebrated every year on the Saturday following the feast of Corpus Christi (in June).
Here is the prayer of Consecration to the Immaculate Heart of Mary:
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Here is the video about Our Lady of Fatima:
About the First Saturdays Devotion requested by Our Lady at Fatima:
The First Saturdays Devotion is offered in reparation for sins against the Immaculate Heart and in consecration to the Immaculate Heart. It consists of 1) receiving communion, 2) going to confession, 3) praying the rosary, and 4) spending 15 minutes mediating on a mystery of the rosary on the first Saturday of 5 consecutive months.