You could certainly get them in by putting the two seperate paragraphs in div tags and then floating one to the left and one to the right.
So you would use this html:
<div id="author">Author Here</div>
<div id="date">02nd January 2015</div>
Obviously changing the contents of the div tags to contain your php. Then using this CSS, you can have them on the same line but one left and one right:
#author {
display: inline-block;
float: left;
}
#date {
display: inline-block;
float: right;
}
Here is how it looks on JSfiddle: http://jsfiddle.net/euaqda3c/