Why does Helen refer to the day as an eventful one in The Story of My Life?

Helen refers to the day as an eventful one because it was on that day that her teacher, Anne Mansfield Sullivan, came into her life.

In Chapter Four, Helen recalls the day as the most important day in all her life. It was the third of March in 1887, and Helen was three months shy of reaching her seventh year of life. She testifies that the moment of her first meeting with Anne Sullivan was one filled with light and love.

Helen remembers that, on that eventful day, Anne Sullivan gave her a doll and opened up the world of language to her by spelling out the word on Helen's hand. On that day, Helen proclaims that she also learned other words, words that made the world a new place for her.

I learned a great many new words that day. I do not remember what they all were; but I do know that mother, father, sister, teacher were among them – words that were to make the world blossom for me, "like Aaron's rod, with flowers." It would have been difficult to find a happier child than I was as I lay in my crib at the close of the eventful day and lived over the joys it had brought me, and for the first time longed for a new day to come.