We calculate the passing of our lives using watches, calendars, diaries, but it is our heartbeat, which is a true measure of our beings. The flow of blood in our veins is more rapid, when we experience strong emotions, when we are excited or anxious and it slows when we are gently relaxed.
A ticking clock is of no use here.
When we experience different places, when we encounter different people, we feel alive at a different rhythm of subsequent heartbeats.
Taking a photograph lasts as long as a single heartbeat.