Index: sys/kern/subr_clock.c
===================================================================
--- sys/kern/subr_clock.c	(revision 327438)
+++ sys/kern/subr_clock.c	(working copy)
@@ -199,6 +199,52 @@ clock_ct_to_ts(struct clocktime *ct, struct timesp
 	return (0);
 }
 
+int
+clock_bcd_to_ts(struct bcd_clocktime *bct, struct timespec *ts)
+{
+	struct clocktime ct;
+
+	/*
+	 * Year may come in as 2-digit or 4-digit.  clock_ct_to_ts() handles the
+	 * century for 2-digit, but we need to decode the century for 4-digit.
+	 */
+	if (validbcd(bct->year)) {
+		if (bct->year <= 0x99)
+			ct.year = FROMBCD(bct->year);
+		else
+			ct.year = FROMBCD(bct->year >> 8) * 100 +
+			    FROMBCD(bct->year & 0xff);
+	} else
+		ct.year = -1;
+
+	/*
+	 * Ensure that all values are valid BCD numbers, to avoid assertions in
+	 * the BCD-to-binary conversion routines.  clock_ct_to_ts() will further
+	 * validate the field ranges (such as 0 <= min <= 59) during conversion.
+	 */
+	if (!validbcd(bct->sec)  || !validbcd(bct->min) ||
+	    !validbcd(bct->hour) || !validbcd(bct->day) ||
+	    !validbcd(bct->mon)  || ct.year == -1) {
+		if (ct_debug) {
+			printf("clock_bcd_to_ts: bad BCD: "
+			    "[%04x-%02x-%02x %02x:%02x:%02x]\n",
+			    bct->year, bct->mon, bct->day,
+			    bct->hour, bct->min, bct->sec);
+		}
+		return (EINVAL);
+	}
+
+	ct.mon  = FROMBCD(bct->mon);
+	ct.day  = FROMBCD(bct->day);
+	ct.hour = FROMBCD(bct->hour);
+	ct.min  = FROMBCD(bct->min);
+	ct.sec  = FROMBCD(bct->sec);
+	ct.dow  = bct->dow;
+	ct.nsec = bct->nsec;
+
+	return (clock_ct_to_ts(&ct, ts));
+}
+
 void
 clock_ts_to_ct(struct timespec *ts, struct clocktime *ct)
 {
@@ -260,6 +306,23 @@ clock_ts_to_ct(struct timespec *ts, struct clockti
 	    ("seconds %d not in 0-60", ct->sec));
 }
 
+void
+clock_ts_to_bcd(struct timespec *ts, struct bcd_clocktime *bct)
+{
+	struct clocktime ct;
+
+	clock_ts_to_ct(ts, &ct);
+
+	bct->year = TOBCD(ct.year % 100) | (TOBCD(ct.year / 100) << 8);
+	bct->mon  = TOBCD(ct.mon);
+	bct->day  = TOBCD(ct.day);
+	bct->hour = TOBCD(ct.hour);
+	bct->min  = TOBCD(ct.min);
+	bct->sec  = TOBCD(ct.sec);
+	bct->dow  = ct.dow;
+	bct->nsec = ct.nsec;
+}
+
 int
 utc_offset(void)
 {
Index: sys/sys/clock.h
===================================================================
--- sys/sys/clock.h	(revision 327438)
+++ sys/sys/clock.h	(working copy)
@@ -60,9 +60,22 @@ extern int tz_dsttime;
 int utc_offset(void);
 
 /*
- * Structure to hold the values typically reported by time-of-day clocks.
- * This can be passed to the generic conversion functions to be converted
- * to a struct timespec.
+ * Structure to hold the values typically reported by time-of-day clocks,
+ * expressed as binary integers (see below for a BCD version).  This can be
+ * passed to the conversion functions to be converted to/from a struct timespec.
+ *
+ * On input, the year is interpreted as follows:
+ *       0 -   69 = 2000 - 2069
+ *      70 -   99 = 1970 - 1999
+ *     100 -  199 = 2000 - 2099 (Supports hardware "century bit".)
+ *     200 - 1969 = Invalid.
+ *    1970 - 9999 = Full 4-digit century+year.
+ *
+ * The dow field is ignored (not even validated) on input, but is always
+ * populated with day-of-week on output.
+ *
+ * clock_ct_to_ts() returns EINVAL if any values are out of range.  The year
+ * field will always be 4-digit on output.
  */
 struct clocktime {
 	int	year;			/* year (4 digit year) */
@@ -79,6 +92,36 @@ int clock_ct_to_ts(struct clocktime *, struct time
 void clock_ts_to_ct(struct timespec *, struct clocktime *);
 
 /*
+ * Structure to hold the values typically reported by time-of-day clocks,
+ * expressed as BCD.  This can be passed to the conversion functions to be
+ * converted to/from a struct timespec.
+ *
+ * The clock_bcd_to_ts() function interprets the values in the year through sec
+ * fields as BCD numbers, and returns EINVAL if any BCD values are out of range.
+ * After conversion to binary, the values are passed to clock_ct_to_ts() and
+ * undergo further validation as described above.  Year may be 2 or 4-digit BCD,
+ * interpreted as described above.  The nsec field is binary.
+ *
+ * The clock_ts_to_bcd() function converts the timespec to BCD values stored
+ * into year through sec.  The value in year will be 4-digit BCD (e.g.,
+ * 0x2017). The mon through sec values will be 2-digit BCD.  The nsec field will
+ * be binary, and the range of dow makes its binary and BCD values identical.
+ */
+struct bcd_clocktime {
+	int	year;			/* year (4 digit year) */
+	int	mon;			/* month (1 - 12) */
+	int	day;			/* day (1 - 31) */
+	int	hour;			/* hour (0 - 23) */
+	int	min;			/* minute (0 - 59) */
+	int	sec;			/* second (0 - 59) */
+	int	dow;			/* day of week (0 - 6; 0 = Sunday) */
+	long	nsec;			/* nano seconds */
+};
+
+int clock_bcd_to_ts(struct bcd_clocktime *, struct timespec *);
+void clock_ts_to_bcd(struct timespec *, struct bcd_clocktime *);
+
+/*
  * Time-of-day clock functions and flags.  These functions might sleep.
  *
  * clock_register and clock_unregister() do what they say.  Upon return from