[LEAPSECS] timekeeping requirements

[Brian Garrett]

----- Original Message ----- 
From: "Rob Seaman" <seaman at noao.edu>
To: "Leap Second Discussion List" <leapsecs at leapsecond.com>
Sent: Monday, March 03, 2008 1:41 PM
Subject: Re: [LEAPSECS] timekeeping requirements



> Brian Garrett wrote:

>

>> I fail to see how precise atomic timekeeping helps them out that  much. 

>> DUT1 can't possibly be a factor for a timekeeping system  intentionally 

>> designed to avoid the need for advanced observation  methods.

>

>

> The deadline for contributions to SPIE proceedings is before the 

> conference.  If we disbelieve the necessity for such a system, we  could 

> consult the literature rather than speculate.  I'm tired of  hearing the 

> wide range of systems for which DUT1 can't possibly be a  factor. 

> Presumably we'll find out in a few years if we can't be  bothered to 

> consider the issue in a professional engineering context  in advance of 

> making new policy.

>

> Rob Seaman

> NOAO


In the case of Islamic observances, it would depend on whether you were 
doing short- or long-term planning.  To determine the date of *this* year's 
Ramadan fast, all you would need to know would be the date on which the new 
moon could reasonably be expected to be visible, and then verify on the 
actual day whether or not it was visible.  For those Muslims who insist on a 
strict interpretation of Sharia, this is all that is required.  However, 
countries such as Saudi Arabia who have to plan around annual events like 
the Hajj require a calendar that is reliable over a year in advance.  The 
dates of observance, reckoned by the Muslim calendar, would depend on the 
position of the sun and moon, calculation of which is affected by delta-T, 
which is resolvable to within one second and therefore influenced by DUT1. 
Somewhat important if you're planning a pilgrimage next year or the year 
after.

Once again, Shaitan is in the details :)


Brian Garrett