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Daylight saving algorithms (slightly OT?)

Discussion in 'Hobby Electronics' started by Bruce Varley, Mar 24, 2007.

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  1. Bruce Varley

    Bruce Varley Guest

    Hi, I'm producing embedded equipment that needs to know about daylight
    saving, which was introduced in WA late last year. The WA arrangement is
    that clocks shift early in the last Sunday of a specified month. That's
    reasonably OK to program into an embedded device, the only nonvolatile
    config you need to put in is the changeover months, and then let the code
    work out the changeover day. My concern is that the rules may change to
    something else that would require me to reburn the code (much harder to do
    in this case). Is anyone aware of any sort of de-facto standard that exists
    for daylight saving changeovers, which specifies the rules, or limits to the
    rules? TIA
  2. The only rule is that there are no rules. Linux systems implement a
    package called, in Debian, tzdata, which contains a zoneinfo directory
    full of files containing the rules, year by year, for each country and
    zone. You could do worse than download the source packages that are
    associated ( and have a read. Handling of changes
    relies on the package being updateable.

    Clifford Heath.
  3. At work we same problem with LED Time - Temperature Signs we make the
    best solution was to have two external buttons to set the Time Zone. If
    the sign is far away we use a simple door remote with up and down
    buttons. Hope that helps
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