<li>Months are to be spelled out in the body of the article, but abbreviated in notes and in genealogical tables.</li>
<li>Centuries are to be styled "20th 20<sup>th</sup> century".</li>
<li>Calendar designation shall be either "BC" or "AD" whenever there may be ambiguity — AD 1957 or 3400 BC, but 2 January 201 AD. Articles set entirely in one era may omit these.</li>