Timestamp not converting to a string

I imported data from excel which has timestamps, i.e. just time for example '7:01 PM' as a matlab number. However, I'm using the datestr() function to convert the matlab date number to a string and I am getting the following error.

Subscript indices must either be real positive integers or logicals.

Error in formatdate (line 158)
            month = char(strrep(month(dtvector(:,2)), '.', '')); %remove period

Error in dateformverify (line 32)
S = char(formatdate([y,mo,d,h,minute,s],dateformstr,islocal));

Error in datestr (line 194)
S = dateformverify(dtnumber, dateformstr, islocal);

This is the code that I used

a = datestr(PM10data.Time);

However, if I use a specific value in the dataset, say a = datestr(PM10data.Time(391)) the code works. Please help me fix this.

I have attached the .mat file which has all the timestamps

Answer 1

[dpb]

Given the error and that load returned a double array, what follows was a logical next step--

>> load timestamps.mat
>> all(isfinite(Time))
ans =
   0
>> any(isnan(Time))
ans =
   1
>> sum(isnan(Time))
ans =
 434
>> Time(isnan(Time))=[];  % ok, so remove those and...
>> ts=datestr(Time);      % now completes as expected...
>>

[dpb]

Of course, this doesn't answer the question as to how you generated the NaN entries, of course; you'll have to research that issue.