Roman numeral hidden (in left-to-right order) in the four longest Across answers

• XLI x VII x VII
• Year of the swine flu epidemic
• International Year of Astronomy year
• 2009, in the credits
• Year Michael Jackson died
• 2009, in Rome
• Time of Obama's swearing-in
• 2009, classically

Wikipedia Word definitions in Wikipedia
MMIX (pronounced em-mix ) is a 64-bit RISC architecture designed by Donald Knuth , with significant contributions by John L. Hennessy (who contributed to the design of the MIPS architecture ) and Richard L. Sites (who was an architect of the Alpha architecture). ...