Subject: [Ietf-calsify] The "other" time discontinuity: leap-seconds

From: lennox at cs.columbia.edu (Jonathan Lennox)
Date: Mon Nov 6 16:41:56 2006

While I was thinking about the DST discontinuities, it occurred to me that
we should also address the "other" time discontinuity, leap-seconds.

My proposal is that iCalendar be completely ignorant of leap-seconds,
i.e. treat time as a fixed-radix 24:60:60 timescale.  (Pedants can treat
this as UT1, TAI, or "POSIX Time", as they like.)

Thus, calendar authors MUST NOT put "60" in the seconds field of a DATE-TIME
value, and the "nominal duration" rules assume that there are always 60
seconds in a minute.

That is, all occurences of each of the following events end at 00:00:00 of
the day after they start (even though there was a leap second at 2005-12-31
23:59:60 UTC):

DTSTART:20051231T235900Z
DURATION:PT1M

DTSTART:20051231T235900Z
DURATION:PT60S

DTSTART:20051231T235900Z
DURATION:PT1M
FREQ=DAILY;COUNT=2

DTSTART:20051231T235900Z
DURATION:PT60S
FREQ=DAILY;COUNT=2

DTSTART:20051230T235900Z
DURATION:PT1M
FREQ=DAILY;COUNT=2

DTSTART:20051230T235900Z
DURATION:PT60S
FREQ=DAILY;COUNT=2

I feel quite confident that this is the behavior you'll see from every
existing calendaring client.

-- 
Jonathan Lennox
[email-masked]