The Church also encourages us to fast on Holy Saturday until after the Easter Vigil.
Holy Thursday - Good Friday - Holy Saturday make up the Easter Triduum and are not strictly part of Lent, but a separate season in itself. It is the holiest time of the liturgical year.
Whether the Holy Saturday fast is just encouraged or is enforced is a matter that is different from diocese to diocese, my diocese has obligated us to observe that fast.
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