[LEAPSECS] Common Calendar Time (CCT) -Brooks Harris

[Clive D.W. Feather]

Brooks Harris said:

> tm_sec + tm_min*60 + tm_hour*3600 + tm_yday*86400 +

> (tm_year???70)*31536000 + ((tm_year???69)/4)*86400 ???

> ((tm_year???1)/100)*86400 + ((tm_year+299)/400)*86400

> 

> This is an *uncompensated-for-leap-seconds* Gregorian calendar counting 

> scheme with an artificially imposed "1970" ("the Epoch") "origin". I 

> like to call it the 1970 *barrier*.


Why is it a barrier? Nothing prevents tm_year being negative; indeed, it's
a signed type.


> But, CAUTION - not all implementations of gmtime() are equally good. 

> I've compiled and tested many versions from the open-source community 

> and many have smoking gun errors. Outright bugs don't help confidence in 

> consistent implementation and contribute to the confusion.


And that's *without* having to test for an event that only happens every
year or two. Which is why software engineers (among others) would like to
get rid of leap seconds.


>> Maybe the way forward would be to introduce a new

>> "elapsedtime_t" type that really does count seconds since the Epoch (to

>> be used in any applications that require duration) and to deprecate

>> arithmetic on time_t values (which is problematic around leap seconds).

> 

> Yes, generally. Getting ANSI c and POSIX standards bodies to change 

> their ways is an uphill battle.


When I was on the ISO C (*NOT* "ANSI c") committee, we looked at the issue.
Then we asked the expert community (that is, you lot), to come up with a
consensus proposal that we could look at. As far as I know, the committee
is still waiting.

(I *did* get the double leap second error removed from ISO C, meaning it
vanished from POSIX as well. Everyone agreed that this had been a simple
misunderstanding of something back when the first version of the C Standard
was being written.)

-- 
Clive D.W. Feather          | If you lie to the compiler,
Email: clive at davros.org     | it will get its revenge.
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