There will be a positive leap second occuring on June 30, 2012.  The EO matrix calculator code was modified in early January 2012 to account for this new leap second change.  The user should notice no discontinuous Earth Orientation due to this leap second issue.

However, the code will not produce an Earth Orientation result at UTC 23:59:60 seconds.  If you require
 that result, please produce results at June 30, 2012 at 23:59:59 and July 1, 2012 at 00:00:00 and int
erpolate between the two.

The official announcment is listed below:


                            U.S. NAVAL OBSERVATORY
                         WASHINGTON, D.C.  20392-5420
                                
                                                               January 06, 2012
                                                                         No. 71

                      TIME SERVICE ANNOUNCEMENT SERIES 14

                                 UTC TIME STEP

1.  The International Earth Rotation and Reference Systems Service (IERS) has 
announced the introduction of a time step to occur at the end of June, 2012.

2.  Coordinated Universal Time (UTC) will be retarded by 1.0s so that the 
sequence of dates of the UTC markers will be:

                       2012 June 30   23h   59m   59s
                       2012 June 30   23h   59m   60s
                       2012 July 01    0h    0m    0s

3.  The difference between UTC and International Atomic Time (TAI) is:

      from 2009 01 Jan, UTC to 2012 01 Jul, UTC:           TAI-UTC= +34s
      from 2012 01 Jul, UTC until further notice:          TAI-UTC= +35s

4.  Information regarding current and predicted values of UT1-UTC is provided 
in IERS Bulletin A. 

5.  UTC and all time scales based on UTC will be affected by this adjustment.  
However, GPS will not be adjusted physically.  For GPS, the leap second 
correction contained within the UTC data of subframe 4, page 18 of the 
navigation message transmitted by satellites will change.

     Before the leap second
     GPS-UTC = +15s (i.e., GPS is ahead of UTC by fifteen seconds)

     After the leap second
     GPS-UTC = +16s (i.e., GPS will be ahead by sixteen seconds)