Time is a pulsation.
It resembles heartbeats: Each heartbeat is a singular phenomenon.
Just because my heart is beating now does not mean that it is going to beat again one second from now.
Every second, life surges forth once again.
In the Kabbalah, this diastolic and systolic feature is called "Ratso-vaShov," outpouring and contraction.
It is characteristic of all forms of psychological and biological life and thus, as the Alter Rebbe points out, is also a feature of the life of time.
It is as though the world has a heart whose continual beating enables the world to live.
Because this beating is continuous, we are not aware of its real, dialectical structure, which is simply a chaining of discontinuities.
Thus, we can define the renewal of time as the emergence of a new heartbeat.
In other words, life is reborn.
Let us note in passing that the word pa'am, which means "beat" in Hebrew, also designates a point in time.
–Rabbi Adin Steinsaltz
From The Seven Lights, p. 9, by Rabbi Adin Steinsaltz