Twentieth.
20th century
Twentieth.
2^20
No. Write either 20th Reunion Classes or 20-Year Reunion Classes.
20th 30th
today
January 20th, 2009 can be written as XX.I.MMIX in Roman numerals.
20th Century Orchestral Music
June 20th 1992? 6.20.92?
4/20/2016
VIII-XX-MMX
Modern music (which came to fruition in the 20th century).