thing that happeded in the 1990s
I went to Juneau.
Not a whole lot. You could probably ignore those three years.
Many things happened
many many things
The construction of the white tower, In London
On the 7th of August quite a few years ago I was born.
The Srebrenica Massacre, also known as the Srebrenica Genocide,
things happened like the plague
A way someone looks at something taking into consideration all of the things that have happened with that thing in the past.
Earth is 5.2 billion years old, many things happened, be more specific :)
A historical period, or era as it's sometimes called, is a period of time that is readily identifiable by particular things, events and or persons that happened or existed during that time.