History Time Glossary and Chronology

Practice flashcards covering the definitions of historical time periods, chronological counting methods for BC and AD, and specific decade/quarter divisions for the 20th century.

BC (Before Christ) Counting

The system where years before the birth of Christ are counted backward, meaning $2000\,BC$ occurred before $500\,BC$.

AD (Anno Domini) Counting

The system where years after the birth of Jesus Christ are counted forward, meaning $500\,AD$ passed before $2000\,AD$ appeared.

Time Glossary

The glossary relating to time terms and their associated periods.

Decade

A period consisting of $10$ years.

Quarter (of a century)

One fourth part of a century, consisting of $25$ years.

First Half (of a century)

The first $50$ years of a century, specifically the period from the $1\text{st}$ year to the $50\text{th}$ year.

Second Half (of a century)

The last $50$ years of a century, specifically the period from the $51\text{st}$ year to the $100\text{th}$ year.

Century

A period consisting of $100$ years.

Millennium

A period consisting of $1,000$ years.

Circa (Ca./C.)

A term used when the exact date is not known to indicate the date is somewhere close to the specified range.

First decade of 20th century AD

The time period spanning from $1901\,AD$ to $1910\,AD$.

Fifth decade of 20th century AD

The time period spanning from $1941\,AD$ to $1950\,AD$.

Eighth decade of 20th century AD

The time period spanning from $1971\,AD$ to $1980\,AD$.

Last decade of 20th century AD

The time period spanning from $1991\,AD$ to $2000\,AD$.

First quarter of 20th century AD

The time period spanning from $1901\,AD$ to $1925\,AD$.

Fourth or last quarter of 20th century AD

The time period spanning from $1975\,AD$ to $2000\,AD$.