It’s the third day, after the saviour’s tomb was found empty. The third day after the evel living has manifested his divinity by showing himself alive to The Holy Virgin Mary (Theotokos) to Mary Magdalene and to few of the Holy Apostles.
The upcoming week is called within the Church The Bright Week
The whole week is a week of a divine spiritual joy which we all the Christians experiens (feels).
God is really graceful to us the sinners in this holy days of the year.