[LEAPSECS] Meeting with Wayne Whyte

[Tony Finch]

On Tue, 1 Feb 2011, Mark Calabretta wrote:

>

> We all deal every day with a non-uniform and variable radix counting

> system - "30 days hath September, ...".


However the Gregorian calendar can be implemented in a few static lines of
code, which is orders of magnitude less than is required to handle dynamic
updates of the leap second table. The two are in no way comparable.

    int greg2rd(int y, int m, int d) {
	if (m > 2) m += 1; else m += 13, y -= 1;
	return y*1461/4 - y/100 + y/400 + m*153/5 + d - 428;
    }

    void rg2greg(int d, int *py, int *pm, int *pd) {
	int y, m;
	d += 305;
	y = d*400/146097 + 1;
	y -= y*1461/4 - y/100 + y/400 > d;
	d -= y*1461/4 - y/100 + y/400 - 31;
	m = d*17/520;
	d -= m*520/17;
	if (m < 11) m += 2;
	else m -= 10, y += 1;
	*py = y, *pm = m, *pd = d;
    }

Tony.
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