Method getWeekday

inst/include/Rcpp/date_datetime/Date.h:81–81

does include 1900 (see Date.cpp)

        int getMonth()   const { return m_tm.tm_mon + 1; }      // makes it 1 .. 12
        int getYear()    const { return m_tm.tm_year; }         // does include 1900 (see Date.cpp)
        int getWeekday() const { return m_tm.tm_wday + 1; }     // makes it 1 .. 7
        int getYearday() const { return m_tm.tm_yday + 1; }     // makes it 1 .. 366

        // 1900 as per POSIX mktime() et al