21 BC

Millennium:	1st millennium BC
Centuries:	2nd century BC 1st century BC 1st century
Decades:	40s BC 30s BC 20s BC 10s BC 0s BC
Years:	24 BC 23 BC 22 BC 21 BC 20 BC 19 BC 18 BC

21 BC in various calendars
Gregorian calendar	21 BC XX BC
Ab urbe condita	733
Ancient Greek era	189th Olympiad, year 4
Assyrian calendar	4730
Bengali calendar	−613
Berber calendar	930
Buddhist calendar	524
Burmese calendar	−658
Byzantine calendar	5488–5489
Chinese calendar	己亥年 (Earth Pig) 2676 or 2616 — to — 庚子年 (Metal Rat) 2677 or 2617
Coptic calendar	−304 – −303
Discordian calendar	1146
Ethiopian calendar	−28 – −27
Hebrew calendar	3740–3741
Hindu calendars
- Vikram Samvat	36–37
- Shaka Samvat	N/A
- Kali Yuga	3080–3081
Holocene calendar	9980
Iranian calendar	642 BP – 641 BP
Islamic calendar	662 BH – 661 BH
Javanese calendar	N/A
Julian calendar	21 BC XX BC
Korean calendar	2313
Minguo calendar	1932 before ROC 民前1932年
Nanakshahi calendar	−1488
Seleucid era	291/292 AG
Thai solar calendar	522–523
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Year 21 BC was either a common year starting on Monday, Tuesday or Wednesday or a leap year starting on Tuesday (link will display the full calendar) of the Julian calendar (the sources differ, see leap year error for further information) and a leap year starting on Sunday of the Proleptic Julian calendar. At the time, it was known as the Year of the Consulship of Lollius and Lepidus (or, less frequently, year 733 Ab urbe condita). The denomination 21 BC for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.