Frederick Augustus II, Grand Duke of Oldenburg
Frederick Augustus II (16 November 1852 in Oldenburg – 24 February 1931 in Rastede) was the last ruling Grand Duke of Oldenburg.
He married Princess Elisabeth Anna of Prussia, daughter of Princess Maria Anna of Anhalt-Dessau and Prince Frederick Charles of Prussia.
After her death, he married Elisabeth Alexandrine of Mecklenburg-Schwerin.
Christian, Duke of Oldenburg
Christian, Duke of Oldenburg( born 1 February 1955) is the head of the Grand Ducal Family of Oldenburg.
Anthony I, Count of Oldenburg
Anthony I, Count of Oldenburg and Delmenhorst( 1505 – 22 January 1573, Oldenburg) was a member of the House of Oldenburg and was the Imperial Count of the Counties of Oldenburg and Delmenhorst within the Holy Roman Empire of German Nation.
His parents were John V, Count of Oldenburg( 1460- 1525) and Anna of Anhalt- Zerbst.
Christian II, Count of Oldenburg
Christian II, Count of Oldenburg( died 1233) was a German nobleman.
He was the ruling Count of Oldenburg from 1209 until his death.
Duchess Altburg of Oldenburg
Duchess Altburg Marie Matilda Olga of Oldenburg (19 May 1903 – 16 June 2001) was a daughter of Frederick Augustus II, Grand Duke of Oldenburg by his second wife Duchess Elisabeth Alexandrine of Mecklenburg-Schwerin
Conrad I, Count of Oldenburg
Conrad I of Oldenburg (died 1347) was the Count of Oldenburg from 1344 to 1347.
He succeeded his brother, John III of Oldenburg.
He was the son of John II of Oldenburg and Hedwig of Diepholz.
Conrad married Ingeborg, the daughter of Count Gerhard IV of Holstein-Plön.
They had four children:
Conrad I of Oldenburg is also a male-line ancestor of Queen Margrethe II of Denmark, King Harald V of Norway, and of Philip, Duke of Edinburgh, and thus of Charles, Prince of Wales, and Prince William, Duke of Cambridge.
Christian III, Count of Oldenburg
Count Christian III of Oldenburg( first attested in 1269 in Oldenburg, – 1285 in Oldenburg) was a ruling Count of Oldenburg.
His parents were John I of Oldenburg and Richeza( or" Rixa") of Hoya- Stumpenhausen.
John VII, Count of Oldenburg
Count John VII of Oldenburg and Delmenhorst( nicknamed" the Dike Builder"; 9 September 1540 in Oldenburg – 12 November 1603 in Oldenburg) was a member of the House of Oldenburg and was the ruling Count of County of Oldenburg from 1573 until his death.
His parents were Count Anthony I of Oldenburg and Sophie of Saxe- Lauenburg.
John V, Count of Oldenburg
John V, Count of Oldenburg and Delmenhorst (also counted as John XIV, including also non-ruling namesake siblings; 1460, Oldenburg – 10 February 1526, Oldenburg) was a member of the House of Oldenburg.
He was the ruling Count of Oldenburg from 1500 to 1526.
His parents were Gerhard VI, Count of Oldenburg and Adelheid of Tecklenburg.
Christian V, Count of Oldenburg
Christian V, Count of Oldenburg( sometimes called" Christian VI"; – after 6 April 1399) was the ruling count of Oldenburg from 1368 until 1398.
He was born sometime before 1347 to Count Conrad I of Oldenburg and Ingeborg of Brunswick.
After his father died in 1368, he ruled Oldenburg jointly with his elder brother Conrad II, and after Conrad II's deaths in 1386, with the latter's son, Maurice II.
He married Agnes of Honstein, and the Danish Royal houses of Oldenburg and Schleswig- Holstein- Sonderburg- Glücksburg descend from him via his son and successor Dietrich, Count of Oldenburg.
Through the dynastic marriages of his descendants, he is an ancestor of many European Royal houses.

Question: When did Duchess Altburg Of Oldenburg's father die?
Answer: 24 February 1931