This is 'White Saturday', apparently called thus because on this day you should whitewash the house. It is also the last day of the Easter fast, so traditionally women spend the day in the kitchen, making ready for the feast tomorrow. Perhaps the most important task is to bake a 'mazanec' (a big fluffy bun in the shape of a bread-loaf, made from sweet yeast dough) that most people will eat for their Sunday breakfast - but for the observing Catholics the 'mazanec' is to be taken to the Mass on Sunday morning to be blessed, because traditionally this blessed 'bread' would then be divided between neighbours and the needy, and pieces of it, together with wine and eggs, would also be given to the fields, the well, and the fruit trees, to insure good harvest, plenty of water and sufficient fruit for the coming year.
On Monday, the feast truly starts. But apart from eating, for the Czechs this is the day when boys and men go from house to house with their specially platted switches (pomlazka) to symbolically whip the girls and women so they would be rejuvenated and fertile, and the women reward this by giving away their decorated eggs. So should you be in Czecho on Monday, you'll hear much joyful screaming and laughter as the boys tease the girls and as the girls enjoy teasing them back, pretending to be hiding from them, only to be 'discovered' and 'whipped'. You can read more about the eggs and the switches in my previous post, 'Easter preparations', of the 8th March.