This Amendment No. 21 amends and supplements the statement on Schedule 13D originally filed by Lazarus Management Company LLC ("Lazarus Management"), Justin B. Borus and Lazarus Investment Partners LLLP ("Lazarus Partners") on August 28, 2012, as amended from time to time (the "Schedule 13D").  This Schedule 13D is also filed on behalf of Lazarus Macro Micro Partners LLLP ("Macro Micro Partners" and collectively with Lazarus Management, Mr. Borus and Lazarus Partners, the "Reporting Persons").  All capitalized terms contained herein but not otherwise defined shall have the meanings ascribed to such terms in the Schedule 13D.  The information set forth in response to each Item below shall be deemed to be a response to all Items where such information is relevant.

Item 3.  Source and Amount of Funds or Other Consideration.

The responses to Items 4, 5 and 6 of the Schedule 13D are incorporated herein by reference.

Item 4.  Purpose of Transaction.

Item 4 of the Schedule 13D is hereby supplemented by adding the following:

On November 13, 2015, Lazarus Partners and the Issuer agreed to extend the maturity date of the promissory note originally issued on April 24, 2015, as amended, in the principal amount of $500,000 that was scheduled to mature on November 13, 2015 to the earlier of (i) November 18, 2015, or (ii) immediately prior to the execution of a definitive agreement between the Issuer and Peachtree Health Management, LLC (d/b/a AEON Clinical Laboratories) regarding the previously reported contemplated acquisition, merger or similar transaction.  No other materials terms were modified.

Item 5.  Interest in Securities of the Issuer.

Item 5 of the Schedule 13D is hereby supplemented by adding the following:

Reference is made to Items 7, 9, 11 and 13 of pages 2-5 of this Schedule 13D, which items are incorporated by reference.  The securities reported on this Schedule 13D that are held by Lazarus Partners consist of 6,680,461 shares of common stock, warrants to purchase an additional 6,233,634 shares of common stock and 200,000 shares of Series D Preferred Stock that are convertible into 1,842,113 shares of common stock.  The securities reported on this Schedule 13D that are held by Macro Micro Partners consist of 7,500 shares of common stock.  The calculation of percentage of beneficial ownership in Item 13 of pages 2-5 was calculated using information from Issuer's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on November 13, 2015, in which the Issuer stated that there were 42,755,942 shares of common stock outstanding as of November 5, 2015.

Item 6.  Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer.

The information disclosed in Item 4 above is incorporated herein by reference.

Item 7.  Material to Be Filed as Exhibits.

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After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated:  November 17, 2015

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This will confirm the agreement by and among the undersigned that the Schedule 13D filed with the Securities and Exchange Commission on or about the date hereof with respect to the beneficial ownership by the undersigned of the common stock, par value $0.001 per share, of Authentidate Holding Corp., a Delaware corporation, is being filed, and all amendments thereto will be filed, on behalf of each of the persons and entities named below in accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended. This Agreement may be executed in two or more counterparts, each of which shall be deemed an original, but all of which together shall constitute one and the same instrument.

Dated:  November 17, 2015