But the 21st birthday changes a person's legal status. Depending on your country and state, you may be able to [drink, drive, join the army, vote, etc.] two days after that birthday (your "age" is 21), when you could not one week earlier (your "age" was 20).
Cosmopolitan: 50 Creative 21st Birthday Party Ideas That You’re Free to Steal
Bravo: Need 21st Birthday Gift Ideas? These Bravo Must-Haves Will Get the Party Started
Need 21st Birthday Gift Ideas? These Bravo Must-Haves Will Get the Party Started
Yahoo: Cheers to 21 Years! 50 Ideas To Make Your 21st Birthday the Most Memorable
Cheers to 21 Years! 50 Ideas To Make Your 21st Birthday the Most Memorable
NDTV: Watch: Parents Turn Their Daughter's 21st Birthday Into A Subway-Themed Party
When you think of birthday parties, you might imagine balloons and cake. But for a girl celebrating her 21st birthday, her parents decided to take it to the next level. They threw a Subway-inspired ...
Wikipedia and WHO, among others, seem quite happy to write "the 21st century" (with small c), and this the form I prefer. But it's your choice and no-one can criticise you for writing "the twenty-first century".
The suffixes -st (e.g. 21st), -nd (e.g. 22nd), -rd (e.g. 23rd), and -th (e.g. 24th) are used. In the Victorian period, these indicators were superscripts (2nd, 34th) under general French influence especially in British English, but by the late 20th century, formatting them on the line was favored. [citation needed] Since the 1990s, the superscript style has been revived somewhat because some ...