Year 28 BC was either a common year starting on Saturday, Sunday or Monday or a leap year starting on Saturday or Sunday of the Julian calendar. At the time, it was known as the Year of the First Consulship of Octavian and Agrippa.
|Millennium:||1st millennium BC|
|Centuries:||2nd century BC – 1st century BC – 1st century|
|Decades:||50s BC 40s BC 30s BC – 20s BC – 10s BC 0s BC 0s|
|Years:||31 BC 30 BC 29 BC – 28 BC – 27 BC 26 BC 25 BC|
|Gregorian calendar||28 BC|
|Ab urbe condita||726|
|Ancient Greek era||188th Olympiad (victor)¹|
|Balinese saka calendar||N/A|
|Chinese calendar||壬辰年 (Water Dragon)|
2669 or 2609
— to —
癸巳年 (Water Snake)
2670 or 2610
|Coptic calendar||−311 – −310|
|Ethiopian calendar||−35 – −34|
|- Vikram Samvat||29–30|
|- Shaka Samvat||N/A|
|- Kali Yuga||3073–3074|
|Iranian calendar||649 BP – 648 BP|
|Islamic calendar||669 BH – 668 BH|
|Julian calendar||28 BC|
|Minguo calendar||1939 before ROC|
|Seleucid era||284/285 AG|
|Thai solar calendar||515–516|
99 or −282 or −1054
— to —
100 or −281 or −1053
- Gaius Julius Caesar Octavian becomes Roman Consul for the sixth time. His partner Marcus Vipsanius Agrippa becomes Consul for the second time.
- May 10 – The earliest dated record of a sunspot by Chinese astronomers.
- The Emilius comet is said to have crashed into modern day Pakistan.