UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                  SCHEDULE 14A

                  Proxy Statement Pursuant to Section 14(a) of
                       the Securities Exchange Act of 1934

Filed by the Registrant  [_]

Filed by a Party other than the Registrant [X]

Check the appropriate box:
[_]   Preliminary Proxy Statement
[_]   CONFIDENTIAL, FOR USE OF THE COMMISSION ONLY (AS PERMITTED BY
       RULE 14a-6(e)(2))
[_]   Definitive Proxy Statement
[_]   Definitive Additional Materials
[X]   Soliciting Material Pursuant to ss.240.14a-12

                              CERIDIAN CORPORATION
--------------------------------------------------------------------------------
                (Name of Registrant as Specified In Its Charter)

                              Pershing Square, L.P.
                            Pershing Square II, L.P.
                       Pershing Square International, Ltd.
--------------------------------------------------------------------------------
    (Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check the appropriate box):
[X]   No fee required.
[_]   Fee computed on table below per Exchange Act Rules 14a-6(i)(1) and 0-11.
      (1) Title of each class of securities to which transaction applies:

          ----------------------------------------------------------------------
      (2) Aggregate number of securities to which transaction applies:

          ----------------------------------------------------------------------
      (3) Per unit price or other underlying value of transaction computed
          pursuant to Exchange Act Rule 0-11 (set forth the amount on which the
          filing fee is calculated and state how it was determined):

          ----------------------------------------------------------------------
      (4) Proposed maximum aggregate value of transaction:

          ----------------------------------------------------------------------
      (5) Total fee paid:

          ----------------------------------------------------------------------
[_]   Fee paid previously with preliminary materials.
[_]   Check box if any part of the fee is offset as provided by Exchange Act
      Rule 0-11(a)(2) and identify the filing for which the offsetting fee was
      paid previously. Identify the previous filing by registration statement
      number, or the Form or Schedule and the date of its filing.
      (1) Amount Previously Paid:

          ----------------------------------------------------------------------
      (2) Form, Schedule or Registration Statement No.:

          ----------------------------------------------------------------------
      (3) Filing Party:

          ----------------------------------------------------------------------
      (4) Date Filed:

          ----------------------------------------------------------------------
          PERSONS WHO ARE TO RESPOND TO THE COLLECTION OF INFORMATION CONTAINED
          IN THIS FORM ARE NOT REQUIRED TO RESPOND UNLESS THE FORM DISPLAYS A
          CURRENTLY VALID OMB CONTROL NUMBER.





FOR IMMEDIATE RELEASE
---------------------


                       PERSHING SQUARE CAPITAL MANAGEMENT
                       COMMENTS ON CERIDIAN'S RESPONSE TO
               ITS NOMINATION OF AN ALTERNATIVE SLATE OF DIRECTORS

January 23, 2007, New York, New York: Pershing Square Capital Management, L.P.
today filed proxy materials identifying its slate of eight candidates for
nomination for the board of directors of Ceridian Corporation (NYSE: CEN) for
this year's annual meeting. These candidates include senior executives from a
wide range of industries including executives with previous senior management
experience in payroll processing at ADP, and payment processing at First Data.
These individuals have strong relevant business, strategic, and legal experience
that should greatly assist Ceridian, its shareholders, and its employees with
the creation of shareholder value and a superior experience for its customers
and employees.

All eight of Pershing's board candidates are independent under Ceridian's board
of director independence guidelines. Furthermore, six of the eight candidates -
those other than Mr. William Ackman and Professor Michael Porter - have no
previous affiliation or relationship with Pershing Square.

With respect to the company's January 23rd press release and its statement that
Pershing "inaccurately characterized a number of comments by Ceridian's Chief
Executive Officer" in its meeting on January 12th, Mr. Ackman stated:

      "Rather than participate in a 'he said, she said' dialogue about our
      previous meeting, we prefer to focus on the future of Ceridian under
      improved governance and better alignment with shareholders' interests. As
      an owner of more than 11% or $450 million of Ceridian's outstanding common
      stock, compared with a nominal amount of stock held by the current board,
      we believe that we and the independent directors have identified the
      appropriate incentives and experience to create superior value for all
      Ceridian shareholders. We look forward to the opportunity for Ceridian
      shareholders to exercise their right to choose whom they would like to
      govern their company."

With respect to the company's suggestion that Pershing's proposed slate may
somehow cause the company "to pursue a potentially costly and disruptive proxy
contest," Mr. Ackman stated:

      "We will endeavor to minimize any disruption to the company. We ask only
      that the company avoid launching ad hominem attacks, dilatory litigation
      tactics, meeting delays, and other techniques that only serve to waste
      corporate resources and frustrate shareholders' right to vote. We intend
      only to propose our nominees, meet and discuss our plans and proposals
      with company




      shareholders, and campaign based on the facts for the privilege of
      representing other shareholders on the board of directors. If the company
      commits to do the same, the disruption and costs associated with the
      upcoming annual meeting vote can be kept to a minimum."

                                  *     *     *

                        PERSHING SQUARE'S BOARD NOMINEES
                        --------------------------------

William A. Ackman, age 40, is the Founder and President of the managing member
of Pershing Square Capital, a registered investment adviser with assets under
management of approximately $3 billion. Prior to forming Pershing Square
Capital, in 1992 Mr. Ackman co-founded Gotham Partners Management Co., LLC, an
investment adviser that managed public and private equity hedge fund portfolios.
In connection with his role at Gotham Partners, Mr. Ackman was actively involved
in the management of a number of its portfolio companies in a variety of
director capacities including serving as Chairman of Imperial Parking
Corporation (a parking service company formerly listed on the AMEX) and Chairman
of First Union Real Estate and Mortgage Investments (now known as Winthrop
Realty Trust, Inc., a REIT (NYSE: FUR)). Mr. Ackman received an MBA from the
Harvard Business School and a Bachelor of Arts magna cum laude from Harvard
College.

Michael L. Ashner, age 54, has been the Chief Executive Officer of Winthrop
Realty Trust, Inc. (NYSE: FUR) since December 31, 2003 and Chairman of the Board
of Directors since April 2004. Mr. Ashner has also served as the Executive
Chairman of Lexington Realty Trust (a New York Stock Exchange listed REIT) and
as the Chairman, President and Chief Executive Officer of Winthrop Realty
Partners, L.P. (a real estate investment and management company) since 1997 and
1995, respectively. Mr. Ashner also has been serving as the Managing Director of
AP-USX LLC, which owns a 2.4 million square foot office tower, since 1998. Since
1981, Mr. Ashner has been the President and principal shareholder of Exeter
Capital Corporation, a privately held real estate investment banking firm. Mr.
Ashner also serves on the Board of Directors and on the Audit Committee of NBTY,
Inc. (manufacturers and distributor of nutritional supplements) and Greate Bay
Hotel and Casino, Inc. (a publicly traded hotel and gaming company). Mr. Ashner
served as a director and Chief Executive Officer of Shelbourne Properties I,
Inc., Shelbourne Properties II, Inc. and Shelbourne Properties III, Inc. (each a
REIT) from August 2002 until their liquidation in April 2004. In addition, Mr.
Ashner served on the Boards of Directors of Interstate Hotel Corporation (a
publicly traded hotel management company acquired by Meristar Hospitality),
Nexthealth, Inc. (a publicly traded resort company acquired by management
group), Burnham Pacific Properties, Inc. (liquidated publicly traded REIT), and
Sizeler Property Investors, Inc. (a New York Stock Exchange publicly traded
REIT).

John D. Barfitt, age 53, is a consultant to various private equity and
investment firms advising on potential acquisitions and investments. From 1979
until 2004, Mr. Barfitt held various positions with Automatic Data Processing,
Inc. (NYSE: ADP), one of the largest providers of computerized transaction
processing, data communication and





information services in the world, including Corporate Vice President from 2003
until 2004 (during which time he helped develop and execute ADP's strategy in
offering BPO Payroll/HR related services), Division President of ADP Employer
Services International from 2000 until 2003 (responsible for all facets of the
employer services business throughout Europe, Asia Pacific and Brazil. ADP's
employer services division is the global market leader of transaction processing
and business process management services for payroll, benefits and human
resources), Division President of ADP Claims Solutions Group (the worldwide
leader of claims processing for property and casualty and related industries in
32 countries) from 1998 until 2000 and Senior Vice President of Automotive
Claims Services from 1996 until 1998. Mr. Barfitt also served as a member on
Automatic Data Processing, Inc.'s Corporate Executive Committee from 1998 until
2003.

Harald Einsmann, Ph.D., age 71, has just completed a 4-year assignment as the
Executive Chairman of Findus AB, the second biggest frozen food company in
Europe, which started with the acquisition by Findus AB of the frozen food
business of Nestle SA. Dr. Einsmann also serves as an Operating Partner and a
member of the Board of Directors and the Investment Committee of EQT (which
wholly owned Findus AB, and has just exited this investment). EQT is a leading
European private equity group sponsored by the Wallenberg Group of Scandinavia
(which includes, among other companies, Ericsson Telephones, ABB Engineering
Group, StoraEnso paper company, SKF roller bearings, AstraZeneca, Gambro
Pharmaceuticals, SEB Bank and Skania Trucks). In addition, Dr. Einsmann serves
as a director of Carlson Group (which includes, among other companies, Radisson
Hotels, Radisson Seven Seas Cruise Ships and Thank God Its Friday Restaurants)
and Checkpoint Systems Incorporated (NYSE: CKP) (where Dr. Einsmann also serves
as a member of its Remuneration and Nomination Committees) in the United States,
Tesco PLC (LON: TSCO) (one of UK's most important and most successful retailers)
in the United Kingdom, Rezidor AB (hotel company) in Scandinavia, and The Bata
Shoe Company in Bermuda. Dr. Einsmann also served as a director of EMI Music
Group (for 13 years until 2006) in the United Kingdom and StoraEnso AB (one of
the world's largest forest and paper product companies, retired from the board
in November 2005) in Scandinavia. Prior to his tenure at EQT, Dr. Einsmann was
the Executive Vice President Europe, Middle East and Africa and a member of
Procter & Gamble's Worldwide Board.

Robert J. Levenson, age 65, is a founder and Managing Member of LENOX Capital
Group, LLC, a private venture capital investment company, focused on early stage
software technology and services. Mr. Levenson began his business career at
Haskins & Sells, Certified Public Accountants (a predecessor of Deloitte), and
then worked for IBM in Cleveland, Ohio. In 1966, he partnered with the founder
of a recently formed data processing services company, Central Data Systems,
Inc., a start-up that floated its initial public offering in 1968 and that was
ultimately acquired by ITEL Corp. At ITEL, Mr. Levenson was Group Executive Vice
President when he resigned in 1980. For the following twenty years, beginning in
1981, Mr. Levenson held senior executive positions at Automatic Data Processing,
Inc. (NYSE: ADP) from 1981 until 1984 and served on ADP's Board of Directors
from 1984 until 1990, Medco Containment Services, Inc. (NASDAQ: MCCS) from 1990
until 1993 and served on Medco's Board of Directors during that time, and First
Data Corp. (NYSE: FDC) from 1993 until 2000 and served on





First Data's Board of Directors from 1992 until 2003. His responsibilities
included general management, strategic planning and corporate development. While
a senior executive at ADP (10 years), revenue grew from $550 million to about
$2.5 billion; at Medco (3 years) from just under $1 billion to $2.2 billion; and
at First Data Corp. (7+ years) from nearly $1 billion to almost $6 billion. Mr.
Levenson's governance experience includes service on several boards of directors
(with committee and chair responsibilities) of public and private companies as
well as not-for-profit organizations. In addition to the foregoing, Mr. Levenson
served on the boards of directors of the following public corporations: Central
Data Systems (NASDAQ) (1966 - 1975), Comnet (NASDAQ) (1992 - 1993), Polyvision
Corp. (AMEX) (1996 - 1997), Broadway & Seymour (NASDAQ) (1996 - 1997), Virtual
Communities, Inc (NASDAQ) (1998 - 2000), Superior Telecom (NYSE) (1996 - 2003),
Vestcom International (NASDAQ) (1998 - 2002), and Emisphere Technologies, Inc.
(NASDAQ) (1998 - 2005). Mr. Levenson also served on the boards of directors of
the following private corporations: KBT Inc. (1990 - 1992), Compliance Inc.
(1992 - 1994), UCB Services Inc. (1994 - 1996), FDI/NISA (FDC JV) (1995 - 2005),
Chase Merchant Services (FDC JV) (1997 - 2005), VIPS (1998 - 2005), and Diopsys,
Inc. (2002 - Present).

Michael E. Porter, age 59, is the Bishop William Lawrence Professor at Harvard
University and chairs the Institute for Strategy and Competitiveness, which was
created jointly by Harvard Business School and Harvard University to further
Professor Porter's work. He has been a member of the Faculty at Harvard Business
School since 1973. Professor Porter currently serves as a director on the
advisory board of Pershing Square Capital, has a profits interest in Pershing
Square Capital and is also a limited partner of Pershing Square. Professor
Porter, the author of 17 books and over 125 articles, is a leading authority on
competitive strategy and the competitiveness and the economic development of
nations, states and regions. Professor Porter created and chairs Harvard
Business School's intensive program for newly appointed CEOs of billion dollar
corporations, which guides new CEOs in assuming leadership, setting their agenda
and addressing issues such as strategy, board governance, communication and
value. Professor Porter has served as a strategy advisor to top management in
numerous leading U.S. and international companies, among them Caterpillar,
DuPont, Procter & Gamble, Royal Dutch Shell, Scotts Miracle-Gro, SYSCO and
Taiwan Semiconductor Manufacturing Company. Professor Porter currently serves as
a public director of Thermo Fisher Scientific, Inc. (NYSE: TMO) and Parametric
Technology Corporation (NASDAQ: PMTC). Professor Porter plays an active role in
U.S. economic policy with the Executive Branch, Congress, international
organizations and private groups, including the U.S. Council on Competitiveness
where he is a member of the Executive Committee. Professor Porter has advised
national leaders in numerous countries, including Canada, India, Ireland, New
Zealand, Nicaragua, Peru, Russia, Singapore, Taiwan, Thailand and the United
Kingdom.

Gregory A. Pratt, age 58, is the Vice Chairman of the Board of Directors of, and
from 1998 until 2002 served as the President and the Chief Executive Officer of,
OAO Technology Solutions, Inc. Mr. Pratt further serves as the Chairman of the
Governance Committee of the Board of Directors of Carpenter Technology Corp.
(NYSE: CRS) and as the Chairman of the Audit Committee of the Board of Directors
of AmeriGas Propane,




Inc. Mr. Pratt founded Enterprise Technology Group, Inc. in 1997 which merged
with OAO in 1998. Mr. Pratt is co-founder of Atari Corp. serving variously as
Chief Financial Officer of Atari Corp. and President of Atari (US) Corp. from
1984 to 1991. From 1991 until 1996, he served as the President and Chief
Operating Officer of Intelligent Electronics, Inc.

Alan Schwartz, age 66, is a Sterling Professor of Law and Professor of
Management at Yale University. Professor Schwartz's academic specialties include
corporate finance and corporate governance, mergers and acquisitions,
bankruptcy, and commercial transactions. He has published numerous articles and
books in these fields and has been identified, by the Institute of Scientific
Information, as being in the top one half of one percent of social scientists
worldwide in total citations. Professor Schwartz has been the President of the
American Law and Economics Association and editor of The Journal of Law,
Economics and Organization. Professor Schwartz also serves as a director of
Cleveland Cliffs Inc. (NYSE: CLF), chairs its Finance Committee and is a member
of its Board Affairs Committee. Professor Schwartz further has served as a
director of Rohn Industries, chaired its Audit Committee and its Board of
Directors.

                                  *     *     *

Pershing Square Capital Management, L.P. is an investment advisor to private
investment funds with approximately $3 billion in capital under management.

ADDITIONAL INFORMATION AND WHERE TO FIND IT

In connection with Ceridian's 2007 Annual Meeting of Stockholders, Pershing
Square Capital Management, L.P. and/or its affiliates expect to file a proxy
statement and other materials with the SEC. Certain materials have already been
filed by Pershing Square Capital Management, L.P. and its affiliates and
investors are urged to read these materials. WE URGE INVESTORS TO READ THE PROXY
STATEMENT AND THESE OTHER MATERIALS CAREFULLY WHEN THEY BECOME AVAILABLE BECAUSE
THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT CERIDIAN AND THE MATTERS TO BE
CONSIDERED AT ITS ANNUAL MEETING. Investors may also obtain a free copy of the
proxy statement and other relevant documents when they become available as well
as other materials filed with the SEC concerning Ceridian at the SEC's website
at http://www.sec.gov.



Contact: William A. Ackman, Pershing Square Capital Management, L.P., (212) 813
3700.