Number
2020 is one of the natural numbers, after 2019 and before 2021.
It is also an even number and a composite number expressed as '2²×5×101'.
In Chinese numerals, it is expressed as '二千二十' and in Roman numerals as 'MMXX'.
The upper two and lower two digits are the same 20, and similar numbers are after 1919 and before 2121.
In pixiv, it is mainly used to mean '2020 AD'.
Calendar
The year 2020 AD is a leap year, starting on Wednesday.
Anno Domini: 2020 A.D.
Japanese calendar: the 2nd year of Reiwa
Buddhist calendar: 2563 B.E.
Sexagenary cycle: Kanoene (庚子)
Nine stars of the zodiac: Venus in the seventh red (七赤金星, Shichiseki Kinsei)
Normal/leap year: Leap year
Previous year: 2019
Next year: 2021