Putting 501 datetime x-ticks would be impossible to read, at least with this example. This creates all of them, nowever only uses 24 for obvious reasons.
Make appropriate changes to use the ones you want —
t = 0:0.01:5;
signal = sin(2*pi*2*t) + sin(2*pi*5*t) + randn(size(t));
imf = emd(signal);
% Plot HHT spectrum
hht(imf, 1/mean(diff(t)), 'FrequencyLimits', [0 5]);
Ax = gca;
xt = Ax.XTick;
N = 501;
xtime = linspace(min(xt), max(xt), N);
DT = datetime(1995,1,1) + years(xtime);
DT.Format = 'dd-MMM-yyyy';
xtnew = linspace(min(xt), max(xt), numel(xt)*4);
xtlnew = linspace(min(DT), max(DT), numel(xt)*4);
Ax.XTick = xtnew;
Ax.XTickLabel = compose('%s',xtlnew);
% Customize plot labels and title
xlabel('Time');
ylabel('Frequency (Hz)');
title('Hilbert-Huang Transform (HHT) Spectrum');
.
