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1670 (MDCLXX) was a common year starting on Wednesday of the Gregorian calendar and a common year starting on Saturday of the Julian calendar, the 1670th year of the Common Era (CE) and Anno Domini (AD) designations, the 670th year of the 2nd millennium, the 70th year of the 17th century, and the 1st year of the 1670s decade. As of the start of 1670, the Gregorian calendar was 10 days ahead of the Julian calendar, which remained in localized use until 1923.
|Ab urbe condita||2423|
|Balinese saka calendar||1591–1592|
|English Regnal year||21 Cha. 2 – 22 Cha. 2|
|Chinese calendar||己酉年 (Earth Rooster)|
4366 or 4306
— to —
庚戌年 (Metal Dog)
4367 or 4307
|- Vikram Samvat||1726–1727|
|- Shaka Samvat||1591–1592|
|- Kali Yuga||4770–4771|
|Japanese calendar||Kanbun 9|
|Julian calendar||Gregorian minus 10 days|
|Minguo calendar||242 before ROC|
|Thai solar calendar||2212–2213|
1796 or 1415 or 643
— to —
1797 or 1416 or 644
|Wikimedia Commons has media related to 1670.|
- January 21 – French-born highwayman Claude Duval is executed at Tyburn, in London.
- April 29 – Pope Clement X succeeds Pope Clement IX, as the 239th pope.
- May 2 – The Hudson's Bay Company is founded in England, to operate in Canada.
- May 26 – At Dover, England, Charles II of England and Louis XIV of France sign the Secret Treaty of Dover, ending hostilities between their kingdoms. Louis will give Charles 200,000 pounds annually. In return Charles will relax the laws against Catholics, gradually re-Catholicize England, support French policy against the Dutch, and convert to Catholicism himself.
- June 1 – In Dover, England, Charles II of England and Louis XIV of France sign the Secret Treaty of Dover, which will force England into the Third Anglo-Dutch War.
- June 15 – The first stone of Fort Ricasoli is laid down in Malta.
- July 18 (July 8, O.S.) – Treaty of Madrid (1670): Spain recognises Jamaica and the Cayman Islands as English possessions.
- August – Spanish frigates attack Charleston, South Carolina.
- September 1–5 – William Penn and William Mead are tried in London, after a Quaker sermon.
- November 24 – Louis XIV of France authorises work to commence on the construction of Les Invalides, a veterans' hospital in Paris, France.
- December 15 – Welsh privateer in English service, Henry Morgan, recaptures Santa Catalina Island, Colombia.
- December 27 – Henry Morgan captures Fort San Lorenzo, on Panama's Caribbean coast.
- Stenka Razin begins the rebellion of Cossacks in Ukraine.
- Niani, capital of the Mali Empire, is sacked by the Bambara people of the emerging Segou Empire.
- The first French settlers arrive on the Petite Côte, of modern-day Senegal.
- January 24 – William Congreve, English playwright (d. 1729)
- February 25 – Maria Margarethe Kirch, German astronomer (d. 1720)
- February 28 – Benjamin Wadsworth, American president of Harvard University (d. 1737)
- May 8 – Charles Beauclerk, 1st Duke of St Albans, English soldier (d. 1726)
- May 12 – King Frederick Augustus I of Poland (d. 1733)
- June 22 – Eva von Buttlar, German mystic sectarian (d. 1721)
- July 18 – Giovanni Bononcini, Italian composer (d. 1747)
- July 19 – Richard Leveridge, English bass player, composer (d. 1758)
- August 21 – James FitzJames, 1st Duke of Berwick, French military commander (d. 1734)
- November 15 – Bernard Mandeville, Dutch-born economic philosopher (d. 1733)
- November 30 – John Toland, Irish philosopher (d. 1722)
- December 4 – John Aislabie, English politician, director of the South Sea Company (d. 1742)
- date unknown – Sultan Abdullah Khan Abdali, Persian Governor of Herat, Shah of Herat (d. 1721)
- January 3 – George Monck, 1st Duke of Albemarle, English soldier (b. 1608)
- January 6
- Sir Gilbert Gerard, 1st Baronet of Harrow on the Hill, English politician (b. 1587)
- Charles of Sezze, Italian Franciscan friar and saint (b. 1613)
- January 21 – Honorat de Bueil, seigneur de Racan, French aristocrat (b. 1589)
- January 25 – Nicholas Francis, Duke of Lorraine (b. 1609)
- February 9 – King Frederick III of Denmark (b. 1609)
- February 12 – Niklaus Dachselhofer, Swiss politician (b. 1595)
- February 17 – Elizabeth Barnard, Granddaughter of William Shakespeare (b. 1608)
- March 1 – Giovanna Maria Bonomo, beatified Italian Catholic nun (b. 1606)
- March 2 – François-Henri Salomon de Virelade, French lawyer (b. 1620)
- March 10
- March 15 – John Davenport, Connecticut pioneer (b. 1597)
- March 31 – Jacob Westerbaen, Dutch poet (b. 1599)
- April – Ahom King Swargadeo Chakradhwaj Singha or Supangmung of Assam, India
- April 5 – Leonora Baroni, Italian singer (b. 1611)
- April 12 – George, Duke of Brunswick-Lüneburg (b. 1582)
- April 23 – Loreto Vittori, Italian singer and composer (b. 1600)
- May 10 – Claude Vignon, French painter (b. 1593)
- May 21
- May 19 – Ferdinando Ughelli, Italian Cistercian monk, church historian (b. 1595)
- May 23 – Ferdinando II de' Medici, Grand Duke of Tuscany (b. 1610)
- May 31 – Josceline Percy, 11th Earl of Northumberland, English noble (b. 1644)
- June 12 – Hasanuddin of Gowa, 16th Ruler of The Sultanate of Gowa (b. 1631)
- June 25 – Lorens von der Linde, Swedish field marshal (b. 1610)
- June 27 – Thomas Bennet, successful English civil lawyer (b. 1592)
- June 28 – Hendrik Martenszoon Sorgh, Dutch painter (b. 1610)
- June 30
- July 16 – Abraham Diepraam, Dutch painter (b. 1622)
- August 24 – William Neile, English mathematician and founder member of the Royal Society (b. 1637)
- September 11 – Jeanne Chezard de Matel, French mystic (b. 1596)
- September 16 – William Penn, English admiral and politician (b. 1621)
- September 26 – Abraham Teniers, Flemish painter (b. 1629)
- September 28 – Alexander Morus, Franco-Scottish Calvinist preacher (b. 1616)
- August 10 – Richard Ottley, English politician (b. 1626)
- October 3 – Sir Henry Yelverton, 2nd Baronet, English Member of Parliament (b. 1633)
- October 27 – Vavasor Powell, Welsh non-conformist leader (b. 1617)
- November 8 – Emmanuel, Prince of Anhalt-Köthen, German prince of the House of Ascania (b. 1631)
- November 15 – Comenius, Czech writer (b. 1592)
- November 21 – William VII, Landgrave of Hesse-Kassel (b. 1651)
- November 22 – Landgravine Sophie of Hesse-Kassel, Countess of Schaumburg-Lippe (b. 1615)
- December 4 – Emilie of Oldenburg-Delmenhorst, Regent of Schwarzburg-Rudolstadt (1646–1662) (b. 1614)
- Date unknown:
- Alena Arzamasskaia, Russian rebel leader (b. year unknown)