In this week's Torah portion of Bo, we are introduced to the deep relationship between the Jewish people and the moon. "This month shall be to you the head of the months; to you it shall be the first of the months of the year." (Ex. 12:2)
Why doesn't the Torah give the month's names but only says "first of the months" or "second month"? The Ramban teaches that that all of Israel will count months starting from this first month together, and that all subsequent months of the year will be counted back to this time.
In this way each month serves as a zikaron, a remembrance, back to the miracle of the Exodus from Egypt. While later we adopted names for the Jewish months, their essence is their relationship with the Exodus.
We also see that in Judaism we don't use names for the days of the week, but count the days in relation to Shabbat. Day one, day two, day three, until we get to Shabbat. In this way, each day serves as a zikaron, of Shabbat.
Just as the Jewish people could not have existed without the Exodus from Egypt, the Jewish people cannot exist without a relationship with Shabbat.
The more we invest in our relationship with Shabbat, the deeper, more meaningful and rewarding is our Jewish existence.