1. The Battle of Groton Heights occurred on December 30, 1781. During the American Revolution, British forces attacked the town of Groton and its fortifications, resulting in the deaths of over 80 Americans.

2. The Connecticut State Legislature passed a law on December 30, 1800, establishing the practice of daylight saving time. The law required town clocks to be set forward by one hour from the first Sunday in April to the last Sunday in October.

3. On December 30, 1955, Connecticut Governor Abraham Ribicoff signed a bill abolishing the death penalty in the state. It was the first state to do so since Rhode Island in 1852.

4. Connecticut became the sixth state to ratify the United States Constitution on December 30, 1787. The Constitution went into effect on March 4, 1789, after nine states had ratified it.

5. On December 30, 1903, the first successful transatlantic radio transmission was received in the United States. The signal was sent from the Poldhu Wireless Station in England and received by Guglielmo Marconi at his receiving station in South Wellfleet, Massachusetts, which was located close to the Connecticut border.