According to an entry in 'The New York Genealogical and Biographical Record (quarterly-1932) - Extracts' found on Ancestry Auguste died on 2/17/1851. According to another index found on ancestry he was born in 1780.

Wikipedia bio:
Auguste Davezac (May, 1780—February 15, 1851) was an American diplomat who served twice as United States Ambassador to the Netherlands

Auguste Genevieve Valentin D'Avezac was born in May, 1780, near Aux Cayes on the island of Santo Domingo, now Haiti, but then a possession of France. His father was a wealthy landowner, and he was educated in France at the College de Sorèze and the French Military College. In 1791, the slaves of Santo Domingo revolted, which resulted in the deaths of Auguste's two older brothers, with the rest of his family fleeing to Virginia and New Orleans. In 1805 Davezac's sister Louise married Edward Livingston.

Davezac completed his education in France and moved to the United States shortly after his sister's marriage, studying medicine in Edenton, North Carolina and establishing a practice in Accomack County, Virginia. He changed the spelling of his last name (eliminating the apostrophe), decided to abandon medicine for the law and relocated to New Orleans to study under Livingston. Davezac built a successful practice and was a sought-after criminal defense attorney.

During the War of 1812 Davezac served on the local defense committee established by the residents of New Orleans. In 1814 he joined the staff of Andrew Jackson as aide de camp and staff judge advocate with the rank of Major, the title by which he was addressed for the rest of his life. Davezac participated in the Battle of New Orleans. As a result of his War of 1812 experience Davezac became a devoted admirer and political supporter of Jackson, campaigning actively for him in both the 1824 and 1828 campaigns for President.

In 1829 Jackson rewarded Davezac with appointment as Secretary of the United States embassy in the Netherlands, where he served under William Pitt Preble. In 1831 Edward Livingston became Secretary of State and Davezac succeeded Preble, serving as Chargé d'affaires until 1839.

Davezac returned to New Orleans, but soon relocated to New York City, where he was active in Martin Van Buren's unsuccessful 1840 campaign for reelection. In 1841 Davezac was elected to the New York State Assembly as a Democrat, where he served two terms.

In 1844 Davezac supported Van Buren's efforts to win the Democratic nomination for President, and campaigned extensively for the eventual nominee, James K. Polk. When Polk won the presidency, he rewarded Davezac by reappointing him as Chargé d'affaires in the Netherlands, where he served from 1845 to 1850.

After leaving office Davezac returned to New York City, where he lived in retirement for only a few months before he became ill and died on February 15, 1851. He was buried at Calvary Cemetery in Queens.

According to an entry in 'The New York Genealogical and Biographical Record (quarterly-1932) - Extracts' found on Ancestry Auguste died on 2/17/1851. According to another index found on ancestry he was born in 1780.

Wikipedia bio:
Auguste Davezac (May, 1780—February 15, 1851) was an American diplomat who served twice as United States Ambassador to the Netherlands

Auguste Genevieve Valentin D'Avezac was born in May, 1780, near Aux Cayes on the island of Santo Domingo, now Haiti, but then a possession of France. His father was a wealthy landowner, and he was educated in France at the College de Sorèze and the French Military College. In 1791, the slaves of Santo Domingo revolted, which resulted in the deaths of Auguste's two older brothers, with the rest of his family fleeing to Virginia and New Orleans. In 1805 Davezac's sister Louise married Edward Livingston.

Davezac completed his education in France and moved to the United States shortly after his sister's marriage, studying medicine in Edenton, North Carolina and establishing a practice in Accomack County, Virginia. He changed the spelling of his last name (eliminating the apostrophe), decided to abandon medicine for the law and relocated to New Orleans to study under Livingston. Davezac built a successful practice and was a sought-after criminal defense attorney.

During the War of 1812 Davezac served on the local defense committee established by the residents of New Orleans. In 1814 he joined the staff of Andrew Jackson as aide de camp and staff judge advocate with the rank of Major, the title by which he was addressed for the rest of his life. Davezac participated in the Battle of New Orleans. As a result of his War of 1812 experience Davezac became a devoted admirer and political supporter of Jackson, campaigning actively for him in both the 1824 and 1828 campaigns for President.

In 1829 Jackson rewarded Davezac with appointment as Secretary of the United States embassy in the Netherlands, where he served under William Pitt Preble. In 1831 Edward Livingston became Secretary of State and Davezac succeeded Preble, serving as Chargé d'affaires until 1839.

Davezac returned to New Orleans, but soon relocated to New York City, where he was active in Martin Van Buren's unsuccessful 1840 campaign for reelection. In 1841 Davezac was elected to the New York State Assembly as a Democrat, where he served two terms.

In 1844 Davezac supported Van Buren's efforts to win the Democratic nomination for President, and campaigned extensively for the eventual nominee, James K. Polk. When Polk won the presidency, he rewarded Davezac by reappointing him as Chargé d'affaires in the Netherlands, where he served from 1845 to 1850.

After leaving office Davezac returned to New York City, where he lived in retirement for only a few months before he became ill and died on February 15, 1851. He was buried at Calvary Cemetery in Queens.