Tonight we count down from 10 to 0 at midnight and bring in the New Year.
But will it be 2019 when we reach 0? What if there is a leap second?
Quick -- let's check the list of leap seconds provided by the IETF.
No -- it looks good, January 1, 2017 was the last one, and that list is good until June 28, 2019.
Two years ago, things were different.
At "midnight" (UTC), it became 2017.
~ $ perl6 -e 'say DateTime.new("2017-01-01T00:00:00Z").year' 2017
But actually, TWO seconds had passed since 11:59:59 the night (and year) before!
~ $ perl6 -e 'say DateTime.new("2017-01-01T00:00:00Z") - DateTime.new("2016-12-31T23:59:59Z")' 2
Tonight will be fine though:
~ $ perl6 -e 'say DateTime.new("2019-01-01T00:00:00Z") - DateTime.new("2018-12-31T23:59:59Z")' 1
If we want to be more explicit, we can turn
DateTime into an
Instant and back again by using
from-posix -- the latter takes a boolean value as a
second parameter to indicate whether or not leap seconds
should be taken into account.
my $date = DateTime.new("2017-01-01T00:00:00Z"); my $instant = Instant.from-posix: $date.posix, True; my $instant2 = Instant.from-posix: $date.posix; say $instant.DateTime.year; say $instant2.DateTime.year;
I wonder how many languages have native support for leap seconds?