MATLAB: Load date/time data and being recognized for further time related subtraction/addtions

load date/time data

I have a text data file, which includes timestamp like 20150727084239.533 which represent 2015-07-27 08:42:39.533. And I have two questions when dealing with these. 1. how can I use textscan and have it recognized as time? I have the current code shown below, and it only load into the data array as numbers.
Load Vehicle A_0727_L2 Timestamp
filename='Vehicle A_0727_1200.txt';
fid=fopen(filename,'r');
for k=1:2;
  tline=fgetl(fid);                                
end
timestamp1200=zeros(1,7931);
t=1;
while tline~=-1
  datestr=regexp(tline,'(?<=STime="20150727).*(?=" ETime)','match');
  tempdata2=textscan(datestr{1},'%f');
  timestamp1200(:,t)=tempdata2{1};
    t=t+1;
    tline = fgetl(fid);
end
fclose all;
When I use %{HH:mm:ss.FFF}D to replace %f, system returns the following errors:
Error using textscan
Unable to read the DATETIME data with the format 'HH:mm:ss.FFF'. If the
data is not a time, use %q to get string data.
Error in C_July27_L2_Data (line 39)
  tempdata2=textscan(datestr{1},'%{HH:mm:ss.FFF}D');
2. How do I use the load time to perform subtraction like 463 seconds from the loaded data, etc.
thanks!

Best Answer

Try using the datetime function instead of textscan. In your case, you can use the following format:
tempdata2 = datetime(datestr{1}, 'InputFormat', 'yyyyMMddHHmmss.SSS')
Note that this will give you a datetime object. With a datetime object you can perform date arithmetic. To subtract from your date object:
 tempdata2 - seconds(463).
Related Question