It's hard to miss leap years where one day is added to the calendar at the end of February, but you might miss the leap second being added to the clock at 0000 UTC on Jan. 1. In the United States this will take place at 7 p.m. EST and at 4 p.m. PST. Some devices will pick up the time change automatically if they are locked to GPS, the National Bureau of Standards standard time broadcasts, or use network time protocol (NTP) servers locked to the NBS clock.
Stations receiving network or satellite programming during the switch this evening should check with their program provider to see if the second will be added when it officially happens tonight, or whether the change will be delayed.
The ATSC System Time Table (STT) should also be checked. Note that the STT sends GPS time (the count of GPS seconds since 00:00:00 UTC, Jan. 6, 1980) instead of UTC. The "GPS_UTC_Offset" field defines the current offset in seconds between GPS and UTC time standards. This number is subtracted from the GPS time to obtain UTC time.
Based on information on the US Naval Observatory leapsecond web page, the offset on Jan. 1, 2009 will increase to 15 seconds (editor's note: correction from a previous version of this article) from a current value of 14 seconds. Your PSIP generator may not change this number automatically, although if it is using an NTP server the UTC time will change, causing an error in the system time due to the incorrect offset. The ATSC standard allows an error of plus or minus one second.
Failure to catch the leap second shouldn't take stations off the air, but if not handled correctly it could cause automated switching between programming and station breaks to look sloppy. Enjoy your extra second this year!
