Old friends are the best kind

Today I gathered with a small group of people met through my 30 years working at the Calgary Herald. Like most of the people that were there I've known these ladies almost since the beginning. Three of them are dear friends that I see regularly. The fourth moved away and I hadn't seen her in close to 20 years, but you'd never have known to see us all together. She reminded us that she'd only worked there for four years, but that they were four of the most significant years of her life. Which really made me think. If I were to pick a time period to define in those terms, where would I land?