"How can I change the format of the datetime array to military time so that the times may appear in chronological order?"
You don't need to: the Format of datetime objects relates to how the datetime is displayed, and is unrelated to how it is stored internally, so changing how it looks does not change how it will be sorted. If you want chronological order just apply sort and see what happens:
sort(ds)
If you want to change how the datetime is displayed then you can change its Format property. The ISO 8601 date standard is the best to use, as is guarantees chronological order when sorted by character:
T = datetime(...);
T.Format = 'yyyyMMddHHmmss';
