- 45 BC The Julian calendar takes effect for the first time
- 630 The Prophet Muhammad sets out toward Mecca with the army that captures it bloodlessly.
- 1758 The International Commission on Zoological Nomenclature establish the "starting point" for standardized species names across the animal kingdom, based on the binomial nomenclature by Carolus Linnaeus 10th edition of Systema Naturae
- 1863 Emancipation Proclamation issued by Abraham Lincoln to free slaves in US confederate states
- 1896 German physicist Wilhelm Röntgen announces his discovery of x-rays
- 1958 European Economic Community (Common Market) starts operation
1st entry in Samuel Pepys' diary
On January 1, 1660