[tz] Irish Standard Time vs Irish Summer Time

[Random832]

On Fri, Jan 19, 2018, at 02:22, Robert Elz wrote:
>   From: Tom Lane <tgl at sss.pgh.pa.us>
>   Date: Fri, 19 Jan 2018 01:07:18 -0500
>   Subject: Re: [tz] Irish Standard Time vs Irish Summer Time
> 
>   | How, exactly, will it improve anyone's life to change from "tm_isdst = 1
>   | means that local time is advanced" to "tm_isdst means something, but
>   | nobody knows what"?
> 
> The issue is that "means the local time is advanced" is, and always
> has been, an invalid assumption based uon apparent observed behaviour,
> rather than any definition.

It's also based on the plain english meaning of the term "DST" and the words to which the abbreviation expands. Daylight is not being "saved" by turning the clock back.

If it were called tm_isalt (to match the "altzone" global from System V, perhaps), your argument might be more valid, but this name has a clear English meaning, and there is no historical basis (as there is for tm_mon) to justify the failure to match what people expect from reading it.