At what age do you consider someone old?

Here's how I view age stages-

0-12- Baby-Toddler-Child
13-19- Adolescent-Teenager
18-35- Young Adult
36-45- Early Middle Age
46-66-Middle Age
67-75-Retirement Age
76 and up: Old Age

I know for many the age stages are different but this is how I view the stages.
At what age do you consider someone old?
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