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February 1987

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Re: mktime
by seismo!cbpavo.MIS.OH.ATT.COM!mark Feb. 1, 1987

Feb. 1, 1987

I was VERY VERY happy to see mktime, as it turned out to be just what I needed for an application I'm supporting. (Actually, I had to alter it somewhat - the major change was that mktime speaks local time, and I needed a function that spoke UTC. Easy when I had the source, but it's worth mentioning that the UTC flavor is also useful.) What did I need it for? Well, I'm supporting a set of routines that provide X.410 style transactions over a network. These transactions have time stamps in them, and the time stamps are in ASCII, in a format that conforms (almost) to the appropriate ISO standards. These routines are mostly a cut up ctime.c, but I also had to supply functions to take strings received over the network (which are always in UTC) and do things like convert them to local time (for logs and for machines that keep time in local time), add N hours, etc. I'm enclosing the manual pages for my routines (the code itself is, I'm sorry to say, considered proprietary to AT&T, but the interface is open.) I consider this just an expedient solution, and not necessarily the end-all wonderful solution. Note that it does not provide a routine like mktime to the users, since I want to hide the time_t time from the users. (We have to worry about birth dates of parents of people alive today, so the 32 bit time_t isn't adequate. I don't really support that yet, but I don't provide user access to time_t so they won't write code now they'll be sorry for later.) Mark .TH ISODATE 3I .SH NAME isonow \- create ISO format string describing current date/time isodcmp \- compare two ISO format dates iso2local \- convert ISO date to local time iso2gmt \- convert ISO date to UTC time isoadd \- add a fixed offset to an ISO date .SH SYNOPSIS .nf .B "char *" .B "isonow();" .sp .B "int" .B "isodcmp(d1, d2);" .B "char *d1, *d2;" .sp .B "char *" .B "iso2local(date)" .B "char *date;" .sp .B "char *" .B "iso2gmt(date)" .B "char *date;" .sp .B "char *" .B "isoadd(date, days, hours, minutes, seconds)" .B "char *date;" .B "int days, hours, minutes, seconds" .fi .SH DESCRIPTION .P These routines manipulate ISO format date/time strings, as defined in the MDTP specification. Other routines may be added, as needed, later. .P .I isonow returns a character string, in ISO format, describing the current date and time. Only one of the ISO choices is used, namely: .nf yyyymmddhhmmsszzzzzE for example 19850410142954-0500E or 19850410142954+0930E or 19850410192954ZE .fi The first date is in the USA Eastern time zone, the second in the Australian Central time zone, and since isonow always returns GMT, the third sample is more typical. The trailing E means .I exact , as opposed to B for .I before or P for .I post (after.) .P .I isodcmp compares two ISO format times, telling which is earlier. It returns \-1 if the first is earlier, 0 if they are the same, and +1 if the second is earlier. .P .I iso2local takes an ISO format date (in either Z time zone, local time, or any other time zone) and converts it to the local time zone. It returns a string in ISO format indicating the local time zone. .P .I iso2gmt takes an ISO format date (in any time zone) and converts it to the Z (GMT) time zone. It returns a string in ISO format indicating the Z time zone. .P .I isoadd takes an ISO format date (in any time zone) and adds the given number of days, hours, minutes, and seconds to it. The numbers may be positive or negative. It returns a string in ISO format indicating the Z time zone. .SH BUGS In the interests of speed, .I isodcmp does not work correctly if any other variant of ISO format is used (e.g. seconds are missing, or a Z time zone is used, or a precision is included), or if the two time zones are not the same.

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