[LEAPSECS] Local insertion of leap seconds

[Warner Losh]

On Jan 3, 2014, at 1:45 PM, Stephen Scott wrote:


> Subject: Local insertion of leap seconds

> 

> I am new to this group so please excuse if this subject has been previously covered.

> 

> As I understand the standard ITU-R TF.460-6 the leap second correction is instantiated globally as the last second of a UTCZ month.

> 

> However I have not been able to determine any practices for instantiating the leap second correction at other times to avoid such an interruption in the timescale at an inopportune time of day in different locations around the world.


There are one. That's when the leap second happens. It is one of the problems with leap seconds. They are scheduled for a time that's convenient for Europe, not too bad for north/south america, and terrible for Asia.

Warner


> In countries west of Greenwich the insertion happens before midnight making possible to delay the correction to a later and more appropriate time. However in countries east of Greenwich the correction could need to have sufficient advance notice.

> 

> Can you enlighten my understanding of what practices may exist?

> 

> Background for these concerns is compounded by a number of factors.

> 

> 1.)   Television broadcast automation requires precise timing to avoid programs and in particular commercials from being clipped or having gaps.

> 2.)   Video in North America and some other parts of the world is generated on a timescale that is at a frequency of 30/1.001 Hz. This deviation from a SI second timescale means           that a leap second insertion is equivalent to inserting 29.97002997… video frames.

> 3.)   This rate implies in a non-integer number of video frames in a 24 hour day and thus a varying phase alignment to a 24 hour clock.

> 

> Regards

> Stephen

> 

> -- 

> Stephen Scott

> Skotel Corporation

> Brossard, Québec

> Canada

> Mobile:  +1 514-806-2340

> Skype:   SScott2645

> Email:   stephenscott at videotron.ca

>  

>  

> 

> 

>  	

> This email is free from viruses and malware because avast! Antivirus protection is active. 			

> 

> 

> _______________________________________________

> LEAPSECS mailing list

> LEAPSECS at leapsecond.com

> http://six.pairlist.net/mailman/listinfo/leapsecs