Twosday is the name given to Tuesday, February 22, 2022, and an unofficial one-time secular observance held on that day, characterized as a fad. The name is a portmanteau of two and Tuesday, deriving from the fact that the digits of the date form a numeral palindrome marked by exclusivity or prevalence of the digit 2—when written in different numerical date formats, such as: 22/02/2022, 22/2/22 and 2/22/22. It is also an ambigram. According to University of Portland professor Aziz Inan, the palindrome is one of the "ubiquitous palindromes", as it retains its defining characteristics globally, despite the differences in national date formats. In countries that apply the ISO 8601 international standard for the calendar, there is an additional congruence inasmuch as Tuesday is the second day of the week under this scheme.

An ambigram is a calligraphic composition of glyphs that can yield different meanings depending on the orientation of observation. Most ambigrams are visual palindromes that rely on some kind of symmetry, and they can often be interpreted as visual puns.