904
| Years | 
|---|
| Millennium | 
| 1st millennium | 
| Centuries | 
| Decades | 
| Years | 
| 904 by topic | 
|---|
| Leaders | 
| Categories | 
| 
 | 
| Gregorian calendar | 904 CMIV | 
| Ab urbe condita | 1657 | 
| Armenian calendar | 353 ԹՎ ՅԾԳ | 
| Assyrian calendar | 5654 | 
| Balinese saka calendar | 825–826 | 
| Bengali calendar | 310–311 | 
| Berber calendar | 1854 | 
| Buddhist calendar | 1448 | 
| Burmese calendar | 266 | 
| Byzantine calendar | 6412–6413 | 
| Chinese calendar | 癸亥年 (Water Pig) 3601 or 3394 — to — 甲子年 (Wood Rat) 3602 or 3395 | 
| Coptic calendar | 620–621 | 
| Discordian calendar | 2070 | 
| Ethiopian calendar | 896–897 | 
| Hebrew calendar | 4664–4665 | 
| Hindu calendars | |
| - Vikram Samvat | 960–961 | 
| - Shaka Samvat | 825–826 | 
| - Kali Yuga | 4004–4005 | 
| Holocene calendar | 10904 | 
| Iranian calendar | 282–283 | 
| Islamic calendar | 291–292 | 
| Japanese calendar | Engi 4 (延喜4年) | 
| Javanese calendar | 803–804 | 
| Julian calendar | 904 CMIV | 
| Korean calendar | 3237 | 
| Minguo calendar | 1008 before ROC 民前1008年 | 
| Nanakshahi calendar | −564 | 
| Seleucid era | 1215/1216 AG | 
| Thai solar calendar | 1446–1447 | 
| Tibetan calendar | 阴水猪年 (female Water-Pig) 1030 or 649 or −123 — to — 阳木鼠年 (male Wood-Rat) 1031 or 650 or −122 | 
Year 904 (CMIV) was a leap year starting on Sunday of the Julian calendar.