function yd=dd2yd(dd)
% yd=dd2yd(dd) converts drifter 
% day to yearday.
% 4/1/01
dd=dd(:);
gt=greg2(dd-1,1995);
y=gt(:,1);
m=gt(:,2);
d=gt(:,3);
h=gt(:,4);
min=gt(:,5);
s=gt(:,6);
h=h+min./60+s./3600;
yd=julian(y,m,d,h)-julian(y,1,1,0)+1;