diff -Nru busybox-1.21.0/coreutils/Config.src src/coreutils/Config.src
--- busybox-1.21.0/coreutils/Config.src	2013-09-27 14:21:31.330620871 +0200
+++ src/coreutils/Config.src	2013-09-27 14:14:41.771830750 +0200
@@ -555,6 +555,9 @@
 	help
 	  Allow for fractional numeric parameters.
 
+config SLEEPUNTIL
+	bool "sleepuntil"
+
 config SORT
 	bool "sort"
 	default y
diff -Nru busybox-1.21.0/coreutils/Kbuild.src src/coreutils/Kbuild.src
--- busybox-1.21.0/coreutils/Kbuild.src	2013-01-14 05:19:43.000000000 +0100
+++ src/coreutils/Kbuild.src	2013-09-27 14:14:41.771830750 +0200
@@ -64,6 +64,7 @@
 lib-$(CONFIG_SHA512SUM) += md5_sha1_sum.o
 lib-$(CONFIG_SHA3SUM)   += md5_sha1_sum.o
 lib-$(CONFIG_SLEEP)     += sleep.o
+lib-$(CONFIG_SLEEPUNTIL)+= sleepuntil.o
 lib-$(CONFIG_SPLIT)     += split.o
 lib-$(CONFIG_SORT)      += sort.o
 lib-$(CONFIG_STAT)      += stat.o
diff -Nru busybox-1.21.0/coreutils/sleepuntil.c src/coreutils/sleepuntil.c
--- busybox-1.21.0/coreutils/sleepuntil.c	1970-01-01 01:00:00.000000000 +0100
+++ src/coreutils/sleepuntil.c	2013-09-27 14:18:32.497403613 +0200
@@ -0,0 +1,135 @@
+/*
+ * sleepuntil.c for busybox
+ * Created by <nschichan@freebox.fr> on Wed Sep 18 15:41:32 2013
+ */
+
+#include <unistd.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <math.h>
+#include <errno.h>
+
+#include <sys/syscall.h> /* for __NR_clock_gettime */
+
+#include "libbb.h"
+
+//usage:#define sleepuntil_trivial_usage
+//usage:	"sleepuntil -q|<until>"
+//usage:#define sleepuntil_full_usage sleepuntil_trivial_usage
+
+static bool verbose = false;
+
+/*
+ * busybox won't link with -lrt, so use syscall(3) to invoke
+ * clock_gettime(2).
+ */
+static int my_clock_gettime(int clock, struct timespec *ts)
+{
+	return syscall(__NR_clock_gettime, clock, ts);
+}
+
+static void usage(void)
+{
+	printf("usage: sleeptill -q | <timestamp>\n\n");
+}
+
+/*
+ * get CLOCK_MONOTONIC and print it to stdout.
+ */
+static int do_querymode(void)
+{
+	struct timespec ts;
+
+	if (my_clock_gettime(CLOCK_MONOTONIC, &ts) < 0) {
+		perror("clock_gettime");
+		return -1;
+	}
+
+	printf("%u\n", (unsigned int)ts.tv_sec);
+	return 0;
+}
+
+/*
+ * sleep until CLOCK_MONOTONIC reaches the until value.
+ */
+static int do_sleepuntil(const char *str_until)
+{
+	const char *end;
+	unsigned int until;
+	int amount;
+	struct timespec ts;
+
+	until = strtof(str_until, (char**)&end);
+	if (*end) {
+		fprintf(stderr, "%s: invalid until value.", str_until);
+		return -1;
+	}
+
+	if (my_clock_gettime(CLOCK_MONOTONIC, &ts) < 0) {
+		perror("clock_gettime");
+		return -1;
+	}
+
+	amount = until - ts.tv_sec;
+	if (amount <= 0) {
+		/* can't go back to the future (for now) */
+		if (verbose)
+			printf("%i seconds late!\n", -amount);
+		return 0;
+	}
+	if (verbose)
+		printf("must sleep %u seconds.\n", amount);
+
+	ts.tv_sec = amount;
+	ts.tv_nsec = 0;
+
+	/* sleep in a signal friendly way */
+	do {
+		nanosleep(&ts, &ts);
+	} while (errno == EINTR);
+	return 0;
+}
+
+extern int sleepuntil_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int sleepuntil_main(int argc, char **argv)
+{
+	bool querymode = false;
+
+	do {
+		int c = getopt(argc, argv, "qv");
+		if (c < 0)
+			break;
+		switch (c) {
+		case 'q':
+			querymode = true;
+			break;
+		case 'v':
+			verbose = true;
+			break;
+		default:
+			usage();
+			return EXIT_FAILURE;
+		}
+	} while (1);
+
+	argc -= optind;
+	argv += optind;
+
+	if (querymode) {
+		if (do_querymode() < 0)
+			return EXIT_FAILURE;
+		return EXIT_SUCCESS;
+	} else {
+		if (!argc) {
+			usage();
+			return EXIT_FAILURE;
+		}
+		if (do_sleepuntil(argv[0]) < 0)
+			return EXIT_FAILURE;
+		return EXIT_SUCCESS;
+	}
+}
diff -Nru busybox-1.21.0/include/applets.src.h src/include/applets.src.h
--- busybox-1.21.0/include/applets.src.h	2013-01-14 05:19:43.000000000 +0100
+++ src/include/applets.src.h	2013-09-27 14:14:41.775830778 +0200
@@ -335,6 +335,7 @@
 IF_SLATTACH(APPLET(slattach, BB_DIR_SBIN, BB_SUID_DROP))
 /* Do not make this applet NOFORK. It breaks ^C-ing of pauses in shells: */
 IF_SLEEP(APPLET(sleep, BB_DIR_BIN, BB_SUID_DROP))
+IF_SLEEPUNTIL(APPLET(sleepuntil, BB_DIR_BIN, BB_SUID_DROP))
 IF_SOFTLIMIT(APPLET_ODDNAME(softlimit, chpst, BB_DIR_USR_BIN, BB_SUID_DROP, softlimit))
 IF_SORT(APPLET_NOEXEC(sort, sort, BB_DIR_USR_BIN, BB_SUID_DROP, sort))
 IF_SPLIT(APPLET(split, BB_DIR_USR_BIN, BB_SUID_DROP))