d_1 + (y\,\text{years}) + (m\,\text{months}) + (\delta\,\text{days}) = d_2,
\textbf{BusinessDays} = |\{ d\in[d_1,d_2] : d\notin H,\; \text{weekday}(d)\in\{\text{Mon..Fri}\}\}|.
\(\textbf{TotalDays} = d_2 - d_1 + \mathbb{1}_{\{\text{inclusive}\}}\) \(\textbf{Weeks}\,=\,\left\lfloor\dfrac{\text{TotalDays}}{7}\right\rfloor,\quad \textbf{RemainderDays}=\text{TotalDays}\bmod 7\) For calendar breakdown (Years–Months–Days), let \(d_1\) be the start date and \(d_2\) the end date (with \(d_2\ge d_1\)). We find integers \(y,m,\delta\) such that: \[ d_1 + (y\,\text{years}) + (m\,\text{months}) + (\delta\,\text{days}) = d_2,\] with \(0\le m<12\) and \(0\le \delta < \text{daysInMonth}(d_1+y\,\text{years}+m\,\text{months})\). This is computed by advancing years then months, adjusting for month lengths and leap years per Gregorian rules. Business days count excludes Saturdays and Sundays and removes any listed holidays \(H\subseteq[d_1,d_2]\): \[\textbf{BusinessDays} = |\{ d\in[d_1,d_2] : d\notin H,\; \text{weekday}(d)\in\{\text{Mon..Fri}\}\}|.\]