One of the carers asked my mother how old she was and she answered, "Oh, ninetyish..."
In fact she'll be 100 tomorrow.
I just flicked through wikipedia's account of the year 1921 and picked out some cultural/historical landmarks:
In the course of my mother's natal year....
Charlie Chaplin released "The Kid",
Warren Gamaliel Harding was elected President of the United States,
Adolf Hitler became leader of the Nazi party,
Coco Chanel launched Chanel No 5,
And a whole lot of other people who are largely forgotten did a whole lot of other things that seemed important at the time.
Quite a lot has happened since...
It'll be a quiet celebration. There'll be a barbeque. Ailz has looked at the weather forecast and says it's going to be sunny...