Saint Clare Of Assisi Feast Day - 12 August (1255-1969) - 11 August (1970 - present)

Quoted from Wikipedia [1]:

Clare was canonized on 26 September 1255 by Pope Alexander IV, and her feast day was immediately inserted in the General Roman Calendar for celebration on 12 August, the day after her death, as 11 August was already assigned to Saints Tiburtius and Susanna, two 3rd-century Roman martyrs.... The 1969 calendar revision removed the feast of Tiburtius and Susanna from the calendar, finally allowing the memorial of Saint Clare to be celebrated on 11 August, the day of her death.

Quoted in part from Aleteia [2]:

Who was St. Clare?

St. Clare was born in Assisi in the year, 1192. Her parents, Ortulana and Favarone were one of twenty families known as Majors, that is, they were part of the noble, aristocratic class. She grew up in a castle, with servants, next to the cathedral of Assisi, San Rufino.

Her father, Favarone, was a knight. In the early biographies, he appears preoccupied with worldly pursuits. Clare’s mother, on the other hand, was devout and virtuous. With her mother, sisters, servants, and others in the district, the women dedicated themselves to prayer, works of mercy, and service to the poor.

Clare had heard Francis preach in San Rufino, and knew how he and the first brothers lived. She desired to join his movement based on total poverty.

Clare decides to follow Francis

On Palm Sunday, 1212, Clare decided to leave her home with its privileges of wealth and power to become the first woman to follow Francis with only one privilege: Poverty. 

That night, she fled her father’s home and all its earthly privileges, and met Francis and the brothers in a church known as St. Mary of the Angels, also called the Portiuncula. There, Francis gave her the tonsure and crowned her head with a veil – a sign of consecration. 

The same night, the brothers accompanied her to a Benedictine monastery for women known as San Paolo delle Abbadesse. With a Papal interdict prohibiting outsiders from entering the cloister, she would have sanctuary there and be safe from any attempts by her father to take her away. 

Clare’s first miracle

After about two weeks, she moved to a poorer community on the slopes of Mount Subasio known as Sant’Angelo in Panzo. There, she was joined by her sister, Agnes. After Clare’s sister, Agnes, joined her here, the knights of her family came for her, too, and dragged her away violently. Clare went into the chapel and prayed, and her sister’s body became so heavy the knights could not lift her. This was St. This was St. Clare’s first miracle. 

...

Clare’s life in San Damiano

Clare lived in San Damiano for forty years. There, more than fifty sisters joined her there, including her mother and other birth sister.

In San Damiano, Clare fully embraced the life she was called to. She left all the worldly privileges for only one, what she referred to as the Highest Privilege of Poverty. 

[1] https://en.wikipedia.org/wiki/Clare_of_Assisi, quoted without references and hyperlinks.

[2] https://aleteia.org/2021/08/11/a-pilgrimage-in-the-footsteps-of-st-clare-of-assisi/