die Ära
era
A longer, significant period of time shaped by particular events, characteristics, or an influential person.
Die Ära Merkel hat die deutsche Politik für 16 Jahre bestimmt.
The Merkel era shaped German politics for 16 years.

era
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era
A longer, significant period of time shaped by particular events, characteristics, or an influential person.
Die Ära Merkel hat die deutsche Politik für 16 Jahre bestimmt.
The Merkel era shaped German politics for 16 years.

'Ära' (era) is an elevated word for an important and defining period of time. It is not used for everyday time spans, but for epochs in history, politics, or culture that have special significance.
Mit der Erfindung des Internets begann eine neue Ära der Kommunikation.
With the invention of the internet, a new era of communication began.
Common phrases are 'eine Ära prägen' (to shape an era), 'eine neue Ära einleiten' (to usher in a new era), or 'das Ende einer Ära' (the end of an era). An era is often named after a person or characteristic, e.g. 'die Ära der Globalisierung' (the era of globalization).
Der Fall der Berliner Mauer markierte das Ende einer Ära.
The fall of the Berlin Wall marked the end of an era.
You can recognize the geological meaning from technical terms like 'Mesozoikum' (Mesozoic), 'Paläozoikum' (Paleozoic), or words like 'Erdgeschichte' (Earth's history), 'Fossilien' (fossils), and 'Dinosaurier' (dinosaurs). This usage is limited to scientific texts.
Das Mesozoikum wird auch als die Ära der Dinosaurier bezeichnet.
The Mesozoic is also referred to as the era of the dinosaurs.
age
'das Alter' and 'die Ära' can both mean a longer period of time. However, 'die Ära' emphasizes that this time is shaped by special events, features, or an important person. 'das Alter' in this meaning is used more generally for an age or a historical time and is less personally colored. The words can be confused because both talk about long periods of time. If you want to show what made a time special, 'Ära' often sounds more precise.

Mit dem neuen Trainer beginnt für den Verein eine neue Ära.
With the new coach, a new era begins for the club.
Das Buch erzählt vom Alter der Entdeckungsreisen und ihren Folgen.
The book tells of the age of exploration and its consequences.