Re: Predictable Internet Time

Joe Touch <touch@xxxxxxx> · Mon, 2 Jan 2017 22:11:26 -0800



    On 1/1/2017 11:24 AM, Phillip
      Hallam-Baker wrote:

    
      To have a
        complete solution, the way forward would be to require systems
        using PIT to use the 'time smear' approach that has been
        pioneered by Akamai and is now used by Amazon, Google, etc.
        albeit in slightly different and non standard ways.
      

      Using time
        smearing, a program will never emit the time value 12:59:60 as
        demanded by the standard. Instead the leap second is added to
        the machine gradually over the course of 20 or 24 hours. This
        avoids the need to emit a time value that could cause a system
        to fail at the cost of a modest difference between the purported
        and actual value.
    
    
    Smearing leads to differing interpretations of elapsed time for two
    reasons:

    
    1) smearing isn't unambiguously specified

    2) smearing doesn't match the clock standards set by the ITU (who
    defines UTC)

    
    A "complete" solution would have several properties:

    
    - it would always indicate the correct UTC time

    - it would calculate time differences accurately

    
    There's no clear reason why that solution can't be split into parts,
    e.g., using Unix time to calculate time differences and a (complex)
    converter to deal with UTC leap seconds.

    
    Joe