Misaligned timestamps in sample_data.mat?

[cwhanse]

The 10th column is a Matlab timestamp. It appears to me that these timestamps aren't aligned with the data either in local or UTC time.

to recreate:

load('sample_data.mat')
plot(data(1:1200, 10), data(1:1200, 2))
datetick('x')
grid on
xlabel('Time')
ylabel('GHI clear')