mktime/gmtime_r moved and highly simplified

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@1973 42af7a65-404d-4744-a932-0658087f49c3

4 files changed, 689 insertions, 2 deletions

diff --git a/nuttx/lib/Makefile b/nuttx/lib/Makefile
index e00eb5c8c..b2792cdf3 100644
--- a/nuttx/lib/Makefile
+++ b/nuttx/lib/Makefile
@@ -83,6 +83,8 @@ UNISTD_SRCS	+=  lib_chdir.c lib_getcwd.c
 endif
 endif
 
+TIME_SRCS	= lib_mktime.c lib_gmtimer.c lib_timeutils.c
+
 NET_SRCS	= lib_htons.c lib_htonl.c lib_inetntoa.c lib_etherntoa.c
 
 LIBGEN_SRCS	= lib_basename.c lib_dirname.c
@@ -98,8 +100,8 @@ DQ_SRCS		= dq_addlast.c dq_addfirst.c dq_addafter.c dq_addbefore.c \
 DBG_SRCS	= lib_dbg.c lib_dumpbuffer.c
 
 CSRCS		= $(MISC_SRCS) $(STRING_SRCS) $(CTYPE_SRCS) $(STDIO_SRCS) $(STDLIB_SRCS) \
-		  $(MATH_SRCS) $(UNISTD_SRCS) $(NET_SRCS) $(LIBGEN_SRCS) $(REGEX_SRCS) \
-		  $(SQ_SRCS) $(DQ_SRCS) $(DBG_SRCS) 
+		  $(MATH_SRCS) $(UNISTD_SRCS) $(TIME_SRCS) $(NET_SRCS) $(LIBGEN_SRCS) \
+		  $(REGEX_SRCS) $(SQ_SRCS) $(DQ_SRCS) $(DBG_SRCS) 
 COBJS		= $(CSRCS:.c=$(OBJEXT))
 
 SRCS		= $(ASRCS) $(CSRCS)
diff --git a/nuttx/lib/lib_gmtimer.c b/nuttx/lib/lib_gmtimer.c
new file mode 100644
index 000000000..2758acd1a
--- /dev/null
+++ b/nuttx/lib/lib_gmtimer.c
@@ -0,0 +1,310 @@
+/****************************************************************************
+ * lib/lib_gmtimer.c
+ *
+ *   Copyright (C) 2007, 2009 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * 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. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+
+#include <time.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/time.h>
+
+/****************************************************************************
+ * Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Type Declarations
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/* Calendar/UTC conversion routines */
+
+static void   clock_utc2calendar(time_t utc, int *year, int *month, int *day);
+#ifdef CONFIG_GREGORIAN_TIME
+static void   clock_utc2gregorian (time_t jdn, int *year, int *month, int *day);
+
+#ifdef CONFIG_JULIAN_TIME
+static void   clock_utc2julian(time_t jdn, int *year, int *month, int *day);
+#endif /* CONFIG_JULIAN_TIME */
+#endif /* CONFIG_GREGORIAN_TIME */
+
+/**************************************************************************
+ * Public Constant Data
+ **************************************************************************/
+
+/****************************************************************************
+ * Public Variables
+ ****************************************************************************/
+
+/**************************************************************************
+ * Private Variables
+ **************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function:  clock_calendar2utc, clock_gregorian2utc,
+ *            and clock_julian2utc
+ *
+ * Description:
+ *    Calendar to UTC conversion routines.  These conversions
+ *    are based on algorithms from p. 604 of Seidelman, P. K.
+ *    1992.  Explanatory Supplement to the Astronomical
+ *    Almanac.  University Science Books, Mill Valley. 
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_GREGORIAN_TIME
+static void clock_utc2calendar(time_t utc, int *year, int *month, int *day)
+{
+#ifdef CONFIG_JULIAN_TIME
+
+  if (utc >= GREG_DUTC)
+    {
+      clock_utc2gregorian(utc + JD_OF_EPOCH, year, month, day);
+    }
+  else
+    {
+      clock_utc2julian (utc + JD_OF_EPOCH, year, month, day);
+    }
+
+#else /* CONFIG_JULIAN_TIME */
+
+  clock_utc2gregorian(utc + JD_OF_EPOCH, year, month, day);
+
+#endif /* CONFIG_JULIAN_TIME */
+}
+
+static void clock_utc2gregorian(time_t jd, int *year, int *month, int *day)
+{
+  long	l, n, i, j, d, m, y;
+
+  l = jd + 68569;
+  n = (4*l) / 146097;
+  l = l - (146097*n + 3)/4;
+  i = (4000*(l+1))/1461001;
+  l = l - (1461*i)/4 + 31;
+  j = (80*l)/2447;
+  d = l - (2447*j)/80;
+  l = j/11;
+  m = j + 2 - 12*l;
+  y = 100*(n-49) + i + l;
+
+  *year  = y;
+  *month = m;
+  *day   = d;
+}
+
+#ifdef CONFIG_JULIAN_TIME
+
+static void clock_utc2julian(time_t jd, int *year, int *month, int *day)
+{
+  long	j, k, l, n, d, i, m, y;
+
+  j = jd + 1402;
+  k = (j-1)/1461;
+  l = j - 1461*k;
+  n = (l-1)/365 - l/1461;
+  i = l - 365*n + 30;
+  j = (80*i)/2447;
+  d = i - (2447*j)/80;
+  i = j/11;
+  m = j + 2 - 12*i;
+  y = 4*k + n + i - 4716;
+
+  *year  = y;
+  *month = m;
+  *day   = d;
+}
+
+#endif /* CONFIG_JULIAN_TIME */
+#else/* CONFIG_GREGORIAN_TIME */
+
+static void clock_utc2calendar(time_t days, int *year, int *month, int *day)
+{
+  int     value;
+  int     tmp;
+  boolean leapyear;
+
+  /* There must be a better way to do this than the brute for method below */
+
+  value = 70;
+  for (;;)
+    {
+      /* Is this year a leap year (we'll need this later too) */
+
+      leapyear = clock_isleapyear(value + 1900);
+
+      /* Get the number of days in the year */
+
+      tmp = (leapyear ? 366 : 365);
+
+      /* Do we have that many days? */
+
+      if (days >= tmp)
+        {
+           /* Yes.. bump up the year */
+
+           value++;
+           days -= tmp;
+        }
+      else
+        {
+           /* Nope... then go handle months */
+
+           break;
+        }
+    }
+
+  /* At this point, value has the year and days has number days into this year */
+
+  *year = value;
+
+  /* Handle the month */
+
+  value = 0; /* zero-based */
+  for (;;)
+    {
+      /* Get the number of days that occurred before the beginning of the next month */
+
+      tmp = g_daysbeforemonth[value + 1];
+      if (value >= 2 && leapyear)
+        {
+          tmp++;
+        }
+
+      /* Does that equal or exceed the number of days we have remaining? */
+
+      if (tmp >= days)
+        {
+          /* Yes.. this is the one we want.  The 'days' for this number of days that
+           * occurred before this month.
+           */
+
+          days -= g_daysbeforemonth[value];
+          break;
+        }
+      else
+        {
+           /* No... try the next month */
+
+           value++;
+        }
+    }
+
+  /* At this point, value has the month into this year (zero based) and days has
+   * number of days into this month (zero based)
+   */
+
+  *month = value;
+  *day   = days + 1; /* 1-based */
+}
+
+#endif /* CONFIG_GREGORIAN_TIME */
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function:  gmtime_r
+ *
+ * Description:
+ *  Time conversion (based on the POSIX API)
+ *
+ ****************************************************************************/
+
+struct tm *gmtime_r(const time_t *clock, struct tm *result)
+{
+  time_t time;
+  time_t jdn;
+  int    year;
+  int    month;
+  int    day;
+  int    hour;
+  int    min;
+  int    sec;
+
+  /* Get the seconds since the EPOCH */
+
+  time = *clock;
+  sdbg("clock=%d\n", (int)time);
+
+  /* Convert to days, hours, minutes, and seconds since the EPOCH */
+
+  jdn   = time / (24*60*60);
+  time -= (24*60*60) * jdn;
+
+  hour  = time / (60*60);
+  time -= (60*60) * hour;
+
+  min   = time / 60;
+  time -= 60 * min;
+
+  sec   = time;
+
+  sdbg("hour=%d min=%d sec=%d\n",
+       (int)hour, (int)min, (int)sec);
+
+  /* Convert the days since the EPOCH to calendar day */
+
+  clock_utc2calendar(jdn, &year, &month, &day);
+
+  sdbg("jdn=%d year=%d month=%d day=%d\n",
+       (int)jdn, (int)year, (int)month, (int)day);
+
+  /* Then return the struct tm contents */
+
+  result->tm_year = (int)year - 1900;
+  result->tm_mon  = (int)month - 1;
+  result->tm_mday = (int)day;
+  result->tm_hour = (int)hour;
+  result->tm_min  = (int)min;
+  result->tm_sec  = (int)sec;
+
+  return result;
+}
+
diff --git a/nuttx/lib/lib_mktime.c b/nuttx/lib/lib_mktime.c
new file mode 100644
index 000000000..594a0672b
--- /dev/null
+++ b/nuttx/lib/lib_mktime.c
@@ -0,0 +1,149 @@
+/****************************************************************************
+ * lib/lib_mktime.c
+ *
+ *   Copyright (C) 2007, 2009 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * 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. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+
+#include <time.h>
+#include <debug.h>
+
+#include <nuttx/time.h>
+
+/****************************************************************************
+ * Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Type Declarations
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Constant Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function:  mktime
+ *
+ * Description:
+ *  Time conversion (based on the POSIX API)
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_GREGORIAN_TIME
+time_t mktime(struct tm *tp)
+{
+  time_t ret;
+  time_t jdn;
+
+  /* Get the EPOCH-relative julian date from the calendar year,
+   * month, and date
+   */
+
+  jdn = clock_calendar2utc(tp->tm_year+1900, tp->tm_mon+1, tp->tm_mday);
+  sdbg("jdn=%d tm_year=%d tm_mon=%d tm_mday=%d\n",
+       (int)jdn, tp->tm_year, tp->tm_mon, tp->tm_mday);
+
+  /* Return the seconds into the julian day. */
+
+  ret = ((jdn*24 + tp->tm_hour)*60 + tp->tm_min)*60 + tp->tm_sec;
+  sdbg("ret=%d tm_hour=%d tm_min=%d tm_sec=%d\n",
+       (int)ret, tp->tm_hour, tp->tm_min, tp->tm_sec);
+
+  return ret;
+}
+#else
+
+/* Simple version that only works for dates within a (relatively) small range
+ * from the epoch.  It does not handle earlier days on longer days where leap
+ * seconds, etc. apply.
+ */
+
+time_t mktime(struct tm *tp)
+{
+  unsigned int days;
+
+  /* Years since epoch in units of days (ignoring leap years). */
+
+  days = (tp->tm_year - 70) * 365;
+
+  /* Add in the extra days for the leap years prior to the current year. */
+
+  days += (tp->tm_year - 69) >> 2;
+
+  /* Add in the days up to the beginning of this month (ignoring any possible leap day). */
+
+  days += (time_t)g_daysbeforemonth[tp->tm_mon];
+
+  /* Add in the leap day for this year (months are zero based) */
+
+  if (tp->tm_mon >= 2 && clock_isleapyear(tp->tm_year + 1900))
+    {
+      days++;
+    }
+
+  /* Add in the days since the beginning of this month (days are 1-based). */
+
+  days += tp->tm_mday - 1;
+
+  /* Then convert the seconds and add in hours, minutes, and seconds */
+
+  return ((days * 24 + tp->tm_hour) * 60 + tp->tm_min) * 60 + tp->tm_sec;
+}
+#endif /* CONFIG_GREGORIAN_TIME */
+
diff --git a/nuttx/lib/lib_timeutils.c b/nuttx/lib/lib_timeutils.c
new file mode 100644
index 000000000..31404edde
--- /dev/null
+++ b/nuttx/lib/lib_timeutils.c
@@ -0,0 +1,226 @@
+/****************************************************************************
+ * lib/lib_calendar2utc.c
+ *
+ *   Copyright (C) 2007, 2009 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * 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. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+
+#include <time.h>
+#include <debug.h>
+
+#include <nuttx/time.h>
+
+/****************************************************************************
+ * Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Type Declarations
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Constant Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Variables
+ ****************************************************************************/
+
+#ifndef CONFIG_GREGORIAN_TIME
+uint16 g_daysbeforemonth[13] =
+{
+  0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365
+};
+#endif
+
+/****************************************************************************
+ * Private Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function:  clock_gregorian2utc, clock_julian2utc
+ *
+ * Description:
+ *    UTC conversion routines.  These conversions are based
+ *    on algorithms from p. 604 of Seidelman, P. K. 1992.
+ *    Explanatory Supplement to the Astronomical Almanac.
+ *    University Science Books, Mill Valley. 
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_GREGORIAN_TIME
+static time_t clock_gregorian2utc(int year, int month, int day)
+{
+  int temp;
+
+  /* temp = (month - 14)/12; */
+
+  temp = (month <= 2 ? -1:0);
+
+  return (1461*(year + 4800 + temp))/4
+    + (367*(month - 2 - 12*temp))/12
+    - (3*((year + 4900 + temp)/100))/4 + day - 32075;
+}
+
+#ifdef CONFIG_JULIAN_TIME
+static time_t clock_julian2utc(int year, int month, int day)
+{
+  return 367*year
+    - (7*(year + 5001 + (month-9)/7))/4
+    + (275*month)/9
+    + day + 1729777;
+}
+#endif /* CONFIG_JULIAN_TIME */
+#endif /* CONFIG_GREGORIAN_TIME */
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function:  clock_isleapyear
+ *
+ * Description:
+ *    Return true if the specified year is a leap year
+ *
+ ****************************************************************************/
+
+#ifndef CONFIG_GREGORIAN_TIME
+int clock_isleapyear(int year)
+{
+  return year % 400 ? (year % 100 ? (year % 4 ? 0 : 1) : 0) : 1;
+}
+#endif /* !CONFIG_GREGORIAN_TIME */
+
+/****************************************************************************
+ * Function:  clock_calendar2utc
+ *
+ * Description:
+ *    Calendar/UTC conversion based on algorithms from p. 604
+ *    of Seidelman, P. K. 1992.  Explanatory Supplement to
+ *    the Astronomical Almanac.  University Science Books,
+ *    Mill Valley. 
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_GREGORIAN_TIME
+time_t clock_calendar2utc(int year, int month, int day)
+{
+  int dyear;
+#ifdef CONFIG_JULIAN_TIME
+  int isgreg;
+#endif /* CONFIG_JULIAN_TIME */
+
+  /* Correct year & month ranges.  Shift month into range 1-12 */
+
+  dyear = (month-1) / 12;	
+  month -= 12 * dyear;
+  year += dyear;
+
+  if (month < 1)
+    {
+      month += 12;
+      year -= 1;
+    }
+
+#ifdef CONFIG_JULIAN_TIME
+  /* Determine which calendar to use */
+
+  if (year > GREG_YEAR)
+    {
+      isgreg = TRUE;
+    }
+  else if (year < GREG_YEAR)
+    {
+      isgreg = FALSE;
+    }
+  else if (month > GREG_MONTH)
+    {
+      isgreg = TRUE;
+    }
+  else if (month < GREG_MONTH)
+    {
+      isgreg = FALSE;
+    }
+  else
+    {
+      isgreg = (day >= GREG_DAY);
+    }
+
+  /* Calculate and return date */
+
+  if (isgreg)
+    {
+      return clock_gregorian2utc(year, month, day) - JD_OF_EPOCH;
+    }
+  else
+    {
+      return clock_julian2utc (year, month, day) - JD_OF_EPOCH;
+    }
+
+#else /* CONFIG_JULIAN_TIME */
+
+  return clock_gregorian2utc(year, month, day) - JD_OF_EPOCH;
+
+#endif /* CONFIG_JULIAN_TIME */
+}
+#else
+time_t clock_calendar2utc(int year, int month, int day)
+{
+  struct tm t;
+
+  /* mktime can (kind of) do this */
+
+  t.tm_year = year;
+  t.tm_mon  = month;
+  t.tm_mday = day;
+  t.tm_hour = 0;
+  t.tm_min  = 0;
+  t.tm_sec  = 0;
+  return mktime(&t);
+}
+#endif /* CONFIG_GREGORIAN_TIME */
+