[Pershing Square Capital Management, L.P. Letterhead]





                                                                     May 2, 2007



Mr. Gary M. Nelson
Executive Vice President, Chief Administrative Officer,
General Counsel and Corporate Secretary
Ceridian Corporation Headquarters
3311 East Old Shakopee Road
Minneapolis, MN  55425

                    Re: 2007 Annual Meeting of Stockholders



Dear Mr. Nelson:

     As you know, certain funds advised by Pershing Square Capital Management,
L.P. intend to field a slate of alternative directors at Ceridian Corporation's
2007 annual meeting of stockholders. Based on remarks on yesterday's earnings
call, we believe an incorrect statement was made as to when Ceridian's annual
meeting will be held. In your capacity as Ceridian's corporate secretary, we
respectfully request clarification of the date on which Ceridian expects to call
the next annual meeting.

     On yesterday's call, in response to a question concerning the latest date
the annual meeting would be held, Ms. Marinello identified the 13-month
anniversary of last year's meeting as the relevant time frame under Delaware law
for this year's annual meeting and stated the meeting would be held within the
required period. Given that Ceridian's 2006 annual meeting was held on May 11,
2006, this year's annual meeting is required to be held no later than June 11,
2007. We do not believe that this is possible as a theoretical or practical
matter. Without clarification on your part, on the basis of yesterday's call,
the investment community has been and will continue to be misinformed.

     Ceridian originally notified the New York Stock Exchange of record and
meeting dates of February 28 and April 26, 2007, but subsequently advised the
Exchange that those dates would be changed. To our knowledge, no additional
notice has been given. As you know, Ceridian must give the New York Stock
Exchange 10 days advance notice of a record date, and Rule 401.03 of the Listed
Company Manual recommends a minimum of 30 days between the record and meeting
dates. Ceridian must also file its preliminary proxy materials with the
Securities and Exchange Commission 10 days prior to mailing definitive
materials, and no preliminary materials have been filed. In the context of a
contested board election, a solicitation period of less than one month is
virtually unheard of.



Mr. Gary M. Nelson
Page 2 of 2

     Accordingly, we believe that Ceridian cannot, and is not planning to, hold
an annual meeting by June 11 in light of the requirements of the New York Stock
Exchange and the federal securities laws, as well as the practical need to
solicit proxies in a contested election.

     Delaware law takes the annual election process seriously. We, too, view the
exercise of our franchise as fundamental to our investment and of paramount
importance to the future direction of Ceridian's business and affairs. At the
risk of understatement, it would be unfortunate if Ceridian's failure to hold
the 2007 annual meeting on a timely basis is the result of an attempt to
frustrate a stockholder vote.

     As the largest stockholder of Ceridian, we hereby request you to correct
the misimpression left by yesterday's call, and inform all stockholders of when
the annual meeting will be held.

                                   PERSHING SQUARE CAPITAL MANAGEMENT, L.P.

                                   Very truly yours,

                                   /s/ Roy J. Katzovicz

                                   Roy J. Katzovicz


cc: Steven A. Rosenblum, Wachtell, Lipton, Rosen & Katz
    Stephen R. DiPrima, Wachtell, Lipton, Rosen & Katz
    Alan J. Sinsheimer, Sullivan & Cromwell LLP
    Janet T. Geldzahler, Sullivan & Cromwell LLP