The second (s) is the base unit of time in the International System of Units, defined by the vibration frequency of cesium-133 atoms. It serves as the foundation for all time measurements, from clocks and watches to GPS satellites and atomic physics. One second equals exactly 1,000 milliseconds and is divided into 60 seconds per minute.

The week (wk) is a time unit equal to 7 days or 168 hours, serving as the standard organizing period for business cycles, school schedules, and pay periods in most cultures. Project timelines, fitness plans, and recurring events are typically planned on a weekly basis. One week equals exactly 7 days or 604,800 seconds.