<ul>
<li>Quantities of fewer than 100 are spelled out as words, larger amount as digits. Compound numbers are hyphenated, as "twenty-one." There are exceptions, such as ages.</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>