Resolving Multiple Time Scales in the Internet
draft-touch-time-02

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Last updated 2017-06-25 (latest revision 2017-04-17)
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TSGWG                                                          J. Touch
Internet Draft                                                  USC/ISI
Intended status: Best Current Practice                   April 17, 2017
Expires: October 2017

              Resolving Multiple Time Scales in the Internet
                          draft-touch-time-02.txt

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Abstract

   Internet systems use a variety of time scales, which can complicate
   time comparisons and calculations. This document explains these
   various ways of indicating time and explains how they can be used
   together safely. This document is intended as a companion to
   Internet time as discussed in RFC 3339.

Table of Contents

   1. Introduction...................................................2
   2. Conventions used in this document..............................4
   3. Terminology....................................................4
   4. Background.....................................................5
      4.1. Time uses and properties..................................6
      4.2. Time scales...............................................7
      4.3. Comparison of properties..................................8
   5. Computing time.................................................9
      5.1. Conversion................................................9
         5.1.1. Continuous and uniform..............................10
         5.1.2. Uniform but not continuous..........................10
         5.1.3. Not uniform.........................................11
         5.1.4. Ordering............................................12
      5.2. Calculating intervals....................................13
   6. Advice........................................................14
      6.1. Selection advice.........................................14
      6.2. Hazards..................................................14
   7. Security Considerations.......................................15
   8. IANA Considerations...........................................15
   9. References....................................................15
      9.1. Normative References.....................................15
      9.2. Informative References...................................15
   10. Acknowledgments..............................................17

1. Introduction

   A popular proverb reads, "a person with one clock always knows what
   time it is; a person with two clocks is never sure." Unfortunately,
   Internet systems rely on a variety of time references that often
   need to be reconciled. This document attempts to explain this issue
   and provide advice on how to avoid temporal ambiguity.

   There are various standards for expressing time, including Universal
   Coordinated Time (UTC) [ITU02], local time (UTC adjusted for time
   zone location and daylight saving time shifts), and Unix time
   [OG08], as well as many others. Although the Internet has a standard

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   for expressing time [RFC3339], this document explains the
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