“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 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.
Time is both discontinuous and cyclical.
For example, every day there are two cycles of 12 hours forming the hours of the day and the hours of the night.
But no given hour is like another.
Each has its own life, dimension, and tonality.
According to Kabbalists, this reflects the 12 different configurations of the four letters of the Tetragrammaton, the 4-letter name of God.
Each hour is governed by one of these configurations.
In other words, each hour has its own code, a unique code, just the way each instant is unique.
The second cycle is the cycle of days.
Here again each day forms a complete cycle, a self-contained entity, and each morning is a new birth.
This explains the importance of the prayer that celebrates this birth.
In a similar fashion, the week has its cycle, and the month, whose birth is connected to the moon.
Finally, we have the cycle of the year.
However, there is a fundamental difference between this cycle and the others.
All the other temporal organizations are cyclical, but Rosh Hashanah is an absolute beginning.
Recall that ‘shanah’ (year) comes from a root that means ‘doubling,’ ‘repetition.’
Indeed, what happens is a repetition of the act of creation and a total renewal of time.
Time is like a plant.
The year only refines and develops the seed that is born on Rosh Hashanah and that will grow over the entire year.
To borrow a metaphor from computer science, we could say that the ‘program’ of the year is conceptualized and stored in memory on Rosh Hashanah and that the 364 other days of the year are simply spent running the program.
Time is also like the body, in that it obeys the brain.
This is clearly why Rosh Hashanah is called the head–the brain, program, principle–of the year.
Rosh Hashanah is in some ways, a ‘brain-day.’”
–Rabbi Adin Steinsaltz