leap seconds and the stdc library Post: 94268

Sponsored Content

Top Forums UNIX for Advanced & Expert Users leap seconds and the stdc library Post 94268 by jim mcnamara on Wednesday 28th of December 2005 02:50:01 PM

12-28-2005

Registered User

leap seconds and the stdc library

I understand the NTP protocol, so keeping system time updated is not a problem.

Standard C library routines like localtime() take a number of UTC seconds elapsed since the start of the epoch (Jan 1, 1970). These times in seconds can be a filetime, system time, or some other time in the past or the future.

In order to translate the seconds into years, months, days, etc. correctly the routines have to know about leap seconds. Including the one coming up this Dec 31, there are 23 leap seconds since 1970.

How is this accomplished? -- knowing about newly hatched leap seconds?
BTW HPUX 11.00 C runtine does not do this correction.... VAX C did.

Code:

/* leapsecond.c */
#include <time.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
	time_t when=strtoul(argv[1],(char **)0,10);
	struct tm *tmptr=gmtime(&when);
	
	printf("%s\n",asctime(tmptr));
	return 0;
}

gives this result:
kcsdev:/home/jmcnama> leapsecond 0
Thu Jan  1 00:00:00 1970

kcsdev:/home/jmcnama> leapsecond `echo "365*2*86400"|bc`
Sat Jan  1 00:00:00 1972

kcsdev:/home/jmcnama> leapsecond `echo "365*3*86400"|bc`
Sun Dec 31 00:00:00 1972

kcsdev:/home/jmcnama> leapsecond `echo "(365*3*86400)+86400"|bc`
Mon Jan  1 00:00:00 1973

There were two leap seconds in 1972, the translation does not take leap seconds into account.

jim mcnamara

View Public Profile for jim mcnamara

Find all posts by jim mcnamara

7 More Discussions You Might Find Interesting

1. UNIX for Advanced & Expert Users

Insertion of Leap Second

Hi All, We are running the HP-UX 11.11 and Linux AS 3.0. so, shall we need to make any changes for leap second i.e. insert the leap second on 1st Jan 2006 or does the system have some setup which would take care of this automatically. Please advise. Regards, Inder

2. HP-UX

Leap Second

3. UNIX for Dummies Questions & Answers

Leap year K-shell script

I need a k-shell script that tests for leap-year. Does anyone have one at hand, need ASAP!!!

4. UNIX for Dummies Questions & Answers

Number of leap seconds

Is there a function call in std library or unit command that returns the number of current leap seconds? GG

5. Shell Programming and Scripting

unix korn shell leap years problem

Write a function called dateToDays that takes three parameters -a month string such as Sep, a day number such as 18, and a year number such as 1962-and return s the number of days from January 1, 1900, to the date. Notes: I am asking you to account for leap years. my script is not...

6. Fedora

Leap second happening

Have anybody heard about the Leap second problem Leap second :A leap second is a one-second adjustment that is occasionally applied to Coordinated Universal Time (UTC) in order to keep its time of day close to the mean solar time. How could i avoid such thing in my script which i deal with...

7. Solaris

Leap second for year 2015

I hear the Leap second for 2015 will occur on June 30 at 23:59:60 according to the wild rumours from internet the expected impact ranges from crashing to hanging servers. Can anybody share their preparations what they have done for solaris servers? are there any patches to install or workaround?...

LEARN ABOUT OSX

datetime::leapsecond

DateTime::LeapSecond(3) 				User Contributed Perl Documentation				   DateTime::LeapSecond(3)

NAME

       DateTime::LeapSecond - leap seconds table and utilities

VERSION

       version 0.77

SYNOPSIS

	 use DateTime;
	 use DateTime::LeapSecond;

	 print "Leap seconds between years 1990 and 2000 are ";
	 print DateTime::Leapsecond::leap_seconds( $utc_rd_2000 ) -
	       DateTime::Leapsecond::leap_seconds( $utc_rd_1990 );

DESCRIPTION

       This module is used to calculate leap seconds for a given Rata Die day. It is used when DateTime.pm cannot compile the XS version of this
       code.

       This library is known to be accurate for dates until December 2009.

       There are no leap seconds before 1972, because that's the year this system was implemented.

       o   leap_seconds( $rd )

	   Returns the number of accumulated leap seconds for a given day, in the range 0 .. 22.

       o   extra_seconds( $rd )

	   Returns the number of leap seconds for a given day, in the range -2 .. 2.

       o   day_length( $rd )

	   Returns the number of seconds for a given day, in the range 86398 .. 86402.

SEE ALSO

       <http://hpiers.obspm.fr/eop-pc/earthor/utc/leapsecond.html>

       http://datetime.perl.org

AUTHOR

       Dave Rolsky <autarch@urth.org>

COPYRIGHT AND LICENSE

       This software is Copyright (c) 2012 by Dave Rolsky.

       This is free software, licensed under:

	 The Artistic License 2.0 (GPL Compatible)

perl v5.16.2							    2013-08-25						   DateTime::LeapSecond(3)