Following the textscan description more closely does not help:
banktimefileID = fopen('data/bankaccounttime.txt');
bankaccounttime = textscan(banktimefileID,'%{yMd}D')
fclose(banktimefileID);
Error using textscan
Unable to read the DATETIME data with the format 'yMd'. If the
data is not a time, use %q to get string data.
I have found an easier way to do what I want, although it does not answer the question:
booktimes = importdata('data/bankaccounttime.txt');
test1 = num2str(booktimes(1));
datenum(test1,'yymmdd')
ans =
736313.00
