Tips for writing a memoir include selecting one theme to write about rather than telling an entire life story, to begin the story with a teaser to hook the reader and to include details to let the reader picture the story. More important than facts are emotional truths.
A memoir is about a specific part of life: a career, relationship or disease. It is not autobiography, so be selective in deciding what to include.
Telling a story chronologically often does not create suspense or anticipation, so first capture the reader's interest with a highlight or crisis point. A chronological sequence of events can follow that.
Evoke sensations for the reader with details. Choose details that support or give context to the memoir's theme.
The day an event happened may be completely unimportant, or its importance may be in relation to a more relevant event, such as the day you met John. In that case, the timing of the first event only matters because it happened either before or after you met John, with some resulting implication or consequence. Why it matters is more important; an important part of memoir is reflection and the insights gained from events.