Calendar Calculations & Leap Year Algorithms
Determining the duration between two dates requires evaluating UTC millisecond timestamps to prevent daylight saving time distortion:
$$\text{Total Days} = \frac{|T_2 - T_1|}{1000 \times 60 \times 60 \times 24}$$
When adding or subtracting days from a calendar milestone, JavaScript date manipulation shifts month and year boundaries naturally, adhering to leap year February rules.