In order to differentiate the calendars themselves from their monthly titles, let’s set their fonts to one with serifs and one without.

h2 {
+ font-family: Georgia, serif;
  text-align: center;
}
table {
+ font-family: sans-serif;
  text-align: center;
  margin: auto;
}

Here, Georgia and the default sans-serif are a matter of personal choice and style. It is generally a good idea to offer fallback fonts when specifying a font-family, as seen here with Georgia, which will fall back to the browser’s default serif typeface.