/* gmtoff_tm.c - Get offset from GMT by calling gmtime and subtracting $Id: gmtoff_gmtime.c,v 1.5 2005/03/05 00:37:14 dasenbro Exp $ * Copyright (c) 1998-2003 Carnegie Mellon University. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * * 3. The name "Carnegie Mellon University" must not be used to * endorse or promote products derived from this software without * prior written permission. For permission or any other legal * details, please contact * Office of Technology Transfer * Carnegie Mellon University * 5000 Forbes Avenue * Pittsburgh, PA 15213-3890 * (412) 268-4387, fax: (412) 268-7395 * tech-transfer@andrew.cmu.edu * * 4. Redistributions of any form whatsoever must retain the following * acknowledgment: * "This product includes software developed by Computing Services * at Carnegie Mellon University (http://www.cmu.edu/computing/)." * * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. * * */ #include <config.h> /* * Returns the GMT offset of the struct tm 'tm', obtained from 'time'. */ int gmtoff_of(tm, time) struct tm *tm; time_t time; { struct tm local, gmt; struct tm *gtm; long offset; local = *tm; gtm = gmtime(&time); gmt = *gtm; /* Assume we are never more than 24 hours away. */ offset = local.tm_yday - gmt.tm_yday; if (offset > 1) { offset = -24; } else if (offset < -1) { offset = 24; } else { offset *= 24; } /* Scale in the hours and minutes; ignore seconds. */ offset += local.tm_hour - gmt.tm_hour; offset *= 60; offset += local.tm_min - gmt.tm_min; /* Restore the data in the struct 'tm' points to */ *tm = local; return offset * 60; }