We Orthodox have entered the period of the Triodion, whose odd name is explained here. The book includes all the hymns from the pre-Lenten days through Holy Week.
I always feel that the Lenten season has begun when I first hear and sing this hymn, as we did in church yesterday:
Open to me the doors of repentence, O Giver of Life,
for early in the morning my spirit seeks thy holy temple,
bearing the temple of my body all defiled.
But in thy compassion, cleanse it
by thy loving-kindness and great mercy.