From the EO signed by Obama;
http://www.opm.gov/oca/compmemo/2012/2013PAY_Attach.pdf
By the authority vested in me as President by the Constitution and the laws of the United States of America, including section 114(b) of the Continuing Appropriations Resolution, 2013 (Public Law 112175), which provides that any statutory adjustments to current levels in certain pay schedules for civilian Federal employees may take effect on the first day of the first applicable pay period beginning after the date specified in section 106(3) of Public Law 112175, it is hereby ordered as follows:
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Continuing Appropriations Act Passed by Congress in 2012:
http://www.govtrack.us/congress/bills/112/hjres117
Sec. 114. (a) Section 147 of Public Law 111-242, as added by Public Law 111-322, shall be applied by substituting the date specified in section 106(3) of this joint resolution for December 31, 2012 each place it appears.
(b) Notwithstanding any other provision of law, any statutory pay adjustment (as defined in section 147(b)(2) of the Continuing Appropriations Act, 2011 (Public Law 111-242)) otherwise scheduled to take effect during fiscal year 2013 but prior to the date specified in section 106(3) of this joint resolution may take effect on the first day of the first applicable pay period beginning after the date specified in section 106(3).
Introduced Sep 10, 2012
Passed House Sep 13, 2012
Passed Senate Sep 22, 2012
Signed by the President Sep 28, 2012
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Here is a link to EOs regarding pay implementations going back to the end of the Clinton term. They go back beyond Clinton.