• Definitive declaration of biblical canon: Council of Carthage
• Demotic is replaced by Greek
• Constantine I ends persecution of Christians in the Roman Empire; following the death of Julian the Apostate, Christianity is made the official religion of the Empire. The Roman Empire's seat of government is moved to Constantinople.
• Destruction of the Roman Army at the Battle of Adrianople in 378

Significant persons

• Saint Ambrose, bishop of Milan
• Ammianus Marcellinus, Roman Historian
• Emperor Constantine I
• Saint Martin of Tours

Inventions, Discoveries, Introductions

Decades and Years

290s	290	291	292	293	294	295	296	297	298	299
300s	300	301	302	303	304	305	306	307	308	309
310s	310	311	312	313	314	315	316	317	318	319
320s	320	321	322	323	324	325	326	327	328	329
330s	330	331	332	333	334	335	336	337	338	339
340s	340	341	342	343	344	345	346	347	348	349
350s	350	351	352	353	354	355	356	357	358	359
360s	360	361	362	363	364	365	366	367	368	369
370s	370	371	372	373	374	375	376	377	378	379
380s	380	381	382	383	384	385	386	387	388	389
390s	390	391	392	393	394	395	396	397	398	399
400s	400	401	402	403	404	405	406	407	408	409