Okay, I had not experience at all with the Atahualpa theme before taking a look at it to help you with this.
Here’s a simple setup that should work. I downloaded the theme and tested it. You can obviously play with the CSS a bit to style it more how you like, but this does seem to work.
I updated settings on two different Theme Options pages:
First, I went to these settings:
Atahualpa Theme Options – Post & Pages – Edit POST/PAGE INFO ITEMS – BYLINE – Homepage
Atahualpa Theme Options – Post & Pages – Edit POST/PAGE INFO ITEMS – BYLINE – Multi Post Pages
Atahualpa Theme Options – Post & Pages – Edit POST/PAGE INFO ITEMS – BYLINE – Single Post Pages
and added this code to all three:
%date('<\s\p\a\n\ \c\l\a\s\s\=\"\d\a\t\e\"><\s\p\a\n\ \c\l\a\s\s\=\"\m\o\n\t\h\"\>M</\s\p\a\n><\s\p\a\n\ \c\l\a\s\s\=\"\d\a\y\">j</\s\p\a\n><\s\p\a\n\ \c\l\a\s\s\=\"\y\e\a\r\">Y</\s\p\a\n></\s\p\a\n>')%
Then I went to this setting:
Atahualpa Theme Options – Various Content Items – Add HTML/CSS Inserts – CSS Inserts
And added this CSS:
span.date {
display: block;
float: left;
margin: 0 5px 5px 0;
width: 80px;
text-align: center;
border: 1px solid #CCC;
}
span.date span {
display: block;
}
span.date span.month {
font-size: 20px;
background-color: #F00;
color: #FFF;
text-transform: uppercase;
}
span.date span.day {
font-size: 40px;
}
span.date span.year {
font-size: 17px;
letter-spacing: 3px;
}
Hope that helps!