function [istart_A, istop_A, istart_B, istop_B, Aokay] = match_datenum_indices (A, B)
%
% input datenum vectors A and B which can be different lengths
%
% output indices so that both arrays have matching data ranges
% so that:
%   A(istart_A:istop_B) = B(istart_B:istop_B)
% Also
%   istop_A - istart_A == istop_B - istart_B
% If not then Aokay = 0: meaning something is wrong.
% and one of the arrays has a missing value (not evenly spaced in time)
%



