The 24-hour day is based on the axis rotation. The month is based on the lunar cycle and the year is based on the solar cycle.
The calendar is scientific, so what is the 7-day week based on? Rabbi Eli Monsour explains how it’s the ultimate testimony to Hashem’s rulership, outlines the two stages of “yismichu” and “oneg,” and shares how they are relevant every Shabbos.
Watch the rest of the series and more at kiheimchayeinu.com