Reign is he period during which a king or queen occupies the throne (or rules).
The time a monarch rules is his or her reign. However for someone who's in office for a very long time or a time of major social change, you might also hear "period" or "era"...Victorian era, Edwardian period, during Elizabethan times (Elizabeth I).
reign
Queen Elizabeth - I was Queen at that time
Call a Marina, rules are many and various
Queen Elizabeth the I
she was a queen in Iraq 2350 BC, during Soumer time
Isabella
Elizebeth 1
Elizabeth 1
James I
Queen Elizabeth 1 who reigned from 1558 to 1603.
England