Life is years we live. Each year has many different days. Society and different cultures has different traditions, festivals, special days. New Year, Christmas, St Patrick's day. These are not save points in your life.
These dates have no meaning to you, you don‘t remember any of them, am I right? What is meaningful is how you spent the date. The day you graduated from university. Date with first love. The day you made siginificant change in your life. All the things that is directly related to you, gives the date a meaning. The meaning created a save point in your life. Where you can easily travel back, in your mind, of course.
Other things that could create save points of life are books and musics. When I hear a particular song on a special event. I can still remember when I was 14 on a school trip, sitting next to someone and I was listening to that song. I saw my booknote recently then I immediately remembered the time when I read the book. I read the first half when I was on the plane back to Tokyo. That baby behind me was crying. I read the rest when I was on the train going back to Ebisu.
Somehow music and books creates this gate of time and space that brought me back in time, at least in the mind for now. Maybe one day I could travel back in time using these breadcrumbs I spread along the way.