The International Earth Rotation and Reference Systems Service (IERS) announced a positive leap second is to be introduced into the international time scale, Coordinated Universal Time (UTC), at the end of December 2005. The US Naval Observatory released the following information on the leap second.

U.S. NAVAL OBSERVATORY WASHINGTON, D.C. 20392-5420

July 27, 2005
No. 69

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 December, 2005.

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

2005 December 31 23h 59m 59s
2005 December 31 23h 59m 60s
2006 January 01 0h 0m 0s

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

from 1999 01 Jan, UTC to 2006 01 January, UTC: TAI-UTC= +32s
from 2006 01 Jan, UTC until further notice: TAI-UTC= +33s

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, Loran-C and GPS will not be adjusted physically. Times of Coincidence for LORAN-C are available on the Time Service Web Page (http://tycho.usno.navy.mil/loran.html). 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 = +13s (i.e., GPS is ahead of UTC by thirteen seconds)

After the leap second
GPS-UTC = +14s (i.e., GPS will be ahead by fourteen seconds)