321

{| align=right cellpadding=3 id=toc style="margin-left: 15px;"\n|- \n| align="center" colspan=2 | Years:
317 318 319 320 - 321 - 322 323 324 325\n|-\n| align="center" colspan=2 | Decades:
290s 300s 310s - 320s - 330s 340s 350s\n|- \n| align="center" | Centuries:
3rd century - 4th century - 5th century\n|} Events\n*Publication of the first blue law by Constantine I of the Roman Empire: trade is forbidden on Sundays; agriculture is allowed\n*The Roman Catholic church is allowed to hold property Births Deaths \n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n