Removing semicolons from data

I have a dataset from a fitbit that gives e.g. steps per minute. The steps are data I can create an array from but the timedata is between semicolons which seems to give problems. Below is a picture of how the data is presented. And here is the code I used to retrieve it:

str = fileread('12h.json'); % dedicated for reading files as text 
data = jsondecode(str);   % Using the jsondecode function to parse JSON from string to a Matlab struct.
 
step_data = data(1).data.data.activities_steps_intraday;
step_data = struct2cell(step_data);

time = cell2mat(step_data(1,:));
step = cell2mat(step_data(2,:));

How do I create an array for time from this data?

Here is how the data is converted at this moment:

Answer 1

[Matt J]

str = fileread('12h.json'); % dedicated for reading files as text 
data = jsondecode(str);   % Using the jsondecode function to parse JSON from string to a Matlab struct.
 
step_data = data(1).data.data.activities_steps_intraday;
step_data = struct2cell(step_data);

time=datetime(step_data(1,:),'Format','HH:mm:ss')

[Anton]

That is a really easy fix. Thank you!

[Anton]

One extra question: Is there a way to add the date to these timestamps? Because there is no defined date in the timestamps, so it automatically displays the date of today.