1 files changed, 64 insertions, 0 deletions
diff --git a/libc/time/tm_conv.c b/libc/time/tm_conv.c
new file mode 100644
index 0000000..96f4735
--- /dev/null
+++ b/libc/time/tm_conv.c
@@ -0,0 +1,64 @@
+
+#include <time.h>
+
+/* This is a translation from ALGOL in Collected Algorithms of CACM. */
+/* Copied from Algorithm 199, Author: Robert G. Tantzen */
+
+void
+__tm_conv(tmbuf, timep, offset)
+struct tm *tmbuf;
+time_t *timep;
+time_t offset;
+{
+static int   moffset[] =
+   {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334};
+
+   long s;
+   long  j, d, m, y;
+
+   offset += *timep;
+
+   tmbuf->tm_isdst = 0;		/* Someone else can set this */
+
+   j = offset / 86400L + 719469;
+   s = offset % 86400L;
+
+   if( s < 0 ) { s += 86400L; j--; }
+
+   tmbuf->tm_sec = s % 60;
+   tmbuf->tm_min = (s / 60) % 60;
+   tmbuf->tm_hour = s / 3600;
+
+   tmbuf->tm_wday = (j+2) % 7;
+
+   /*
+    * Julian date converter. Takes a julian date (the number of days since
+    * some distant epoch or other), and fills tmbuf.
+    */
+
+   y = (4L * j - 1L) / 146097L;
+   j = 4L * j - 1L - 146097L * y;
+   d = j / 4L;
+   j = (4L * d + 3L) / 1461L;
+   d = 4L * d + 3L - 1461L * j;
+   d = (d + 4L) / 4L;
+   m = (5L * d - 3L) / 153L;
+   d = 5L * d - 3 - 153L * m;
+   d = (d + 5L) / 5L;
+   y = 100L * y + j;
+   if (m < 10)
+      m += 2;
+   else
+   {
+      m -= 10;
+      ++y;
+   }
+
+   tmbuf->tm_year = y - 1900;
+   tmbuf->tm_mon = m;
+   tmbuf->tm_mday = d;
+
+   tmbuf->tm_yday = d + moffset[m];
+   if (m > 1 && ((y) % 4 == 0 && ((y) % 100 != 0 || (y) % 400 == 0)))
+      tmbuf->tm_yday++;
+}