The abbreviation BC (“before Christ”) follows a date, and AD (“anno Domini”) precedes a date. Acceptable alternatives are BCE (“before the common era”) and CE (“common era”), both of which follow a date.
| 40 BC (or 40 BCE) | 4:00 a.m. (or AM) | No. 12 (or no. 12) |
| AD 44 (or 44 CE) | 6:00 p.m. (or PM) | $150 |
Avoid using a.m., p.m., No., or $ when not accompanied by a specific numeral: in the morning (not in the a.m.).