World Eigenvalue Day (light apparel) T-Shirt

What day is World Eigenvalue Day? Everyday is World Eigenvalue Day! There is a song - would you like to hear it? Of course you would. Eigenvalues, sing along As we sing the eigensong EISPACK, LINPACK, Recipes Give us eigens if you please! Eigenvalues are our friend Every time we think of them Normal modes and free vibrations Simplify the computations! Eigenvalues are our hero Make determinants a zero If you need them really quick Invariants will do the trick! Eigenvalues, above all Make the world diagonal If defective you'll be warned 'cause you'll get a Jordan form!