From right to left for recent Aikikai dan certificates (with Heisei as the year and Moriteru Ueshiba sensei as the Doshu):
Column 1: Zaidan Hojin Aikikai
Column 2: Dai (Number) Go = Certificate number for that dan ranking
Column 3: Sho = "Certificate"
Column 4: Your name
Column 5: Migimono konpan aikido: The person on the right is now in aikido
Column 6: (number) dan wo inka su = permitted as (number) dan
Column 7: Heisei (number) nen (number) gatsu (number) nichi = The (number) year of Heisei, (number) month, (number) day
Column 8: Aikido
Column 9: Doshu Ueshiba Moriteru
Column 6 will be worded differently for a fifth dan and up dan certificate by saying "(number) dan kurai ni retsu su" which basically breaks down to "kurai" meaning "to be ranked, placed, occupy a position" and "retsu su" meaning "to rank with, line up with."
For kyu ranked certificates, that column would read, "(number) kyu wo juyo su" which basically means, "(number) kyu has been awarded/granted/conferred."
Hope that helps.