<Tr> <Td> <P> Thirti dayes hath novembir April june and Septembir . Of xxviij is but oon And alle the remenaunt xxx and j </P> </Td> <Td> </Td> <Td> <P> Thirty days have November, April, June, and September . Of 28 is but one And all the remnant 30 and 1 . </P> </Td> </Tr> <P> Thirti dayes hath novembir April june and Septembir . Of xxviij is but oon And alle the remenaunt xxx and j </P> <P> Thirty days have November, April, June, and September . Of 28 is but one And all the remnant 30 and 1 . </P> <P> Variations appeared in Mother Goose and continue to be taught at schools . The unhelpfulness of such involved mnemonics has been parodied as "Thirty days hath September / But all the rest I can't remember" but it has also been called "probably the only sixteenth - century poem most ordinary citizens know by heart". A common nonverbal alternative is the knuckle mnemonic, considering the knuckles of one's hands as months with 31 days and the lower spaces between them as the months with fewer days . Using two hands, one may start from either pinkie knuckle as January and count across, omitting the space between the index knuckles (July and August). The same procedure can be done using the knuckles of a single hand, returning from the last (July) to the first (August) and continuing through . A similar mnemonic is to move up a piano keyboard in semitones from an F key, taking the white keys as the longer months and the black keys as the shorter ones . </P>

When did we start using the roman calendar