Add Space Between Date and Time

In your child theme you can do the following;

Note if you are not using a child theme see here as you should not edit the core files of a theme

You could put them in different divs and add styling to each div.

Example:

<div class="post-date"><?php the_time('j M Y'); ?></div><div class"post-time"><?php the_time('H i'); ?></div>

Then all you need to do is change the css. so in your css if you added

.post-time {
margin-left: 40px
}

This would add a margin of 40px between the date and the time. Obviously that is depending on your current css style of .post-date