[tz] Irish Standard Time vs Irish Summer Time

Joseph Myers jsm at polyomino.org.uk
Sat Jan 20 01:39:50 UTC 2018

On Fri, 19 Jan 2018, Robert Elz wrote:

> "Standard" time is simply the time that is agreed it is *now* (at any 
> time of the year) - that's what it means to be a standard.

That's essentially why I think tm_isdst should be based on something other 
than the notion of one time offset being standard and another being a 
variant on that.  The laws establishing time offsets have the function of 
determining the offset applicable for legal purposes at any given time, 
not the function of determining tm_isdst.  Just because the law happens to 
be worded as "the offset is X, except at these times when it's Y", or to 
give a name involving "standard time" to one choice of offset, should not 
be considered of semantic significance; the law had to choose some part of 
the year to be X and some part to be Y, or if naming the offsets had to 
come up with different names for them, but the particular choice of which 
is X and which is Y is just an arbitrary choice in drafting the law.

Joseph S. Myers
jsm at polyomino.org.uk

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