[time-nuts] When does NIST change to DST?

Nick Sayer nsayer at kfu.com
Mon Mar 14 11:22:40 EDT 2016


Well, then my clock (and perhaps others) is being lazy about interpreting the bits. If it looks at the left bit only, then that would explain early transitions. The other possibility is misreading the right hand bit as being a 1 during one reading and deciding that it had “missed” the change somehow.

> On Mar 13, 2016, at 9:38 PM, Tom Van Baak <tvb at LeapSecond.com> wrote:
> 
> Hi Andy,
> 
> No, there's nothing about 0200Z. Correct, WWVB doesn't know your local zone.
> 
> WWVB itself doesn't "switch" to/from DST. It always only transmits UTC. It is up to your receiver-clock to translate UTC to local time for the user display. This is why most of WWVB radio controlled clocks have a little PMCE (Pacific / Mountain / Central / Eastern) switch.
> 
> The WWVB data format also includes bits which announce if DST change will occur. It is up to the receiver-clock to decode these bits and make the 1 hour adjustment at the appropriate time (usually 2 am local time).
> 
> See also:
> https://en.wikipedia.org/wiki/WWVB
> http://tf.nist.gov/general/pdf/2422.pdf
> http://www.nist.gov/pml/div688/grp40/radioclocks.cfm
> 
> /tvb
> 
> ----- Original Message ----- 
> From: "Andy" <AI.egrps+tn at gmail.com>
> To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
> Sent: Sunday, March 13, 2016 7:21 PM
> Subject: Re: [time-nuts] When does NIST change to DST?
> 
> 
>> I wonder if WWVB switches to DST around 0200Z, maybe?  Since it can't
>> tell where your local zone is.
>> 
>> Andy
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