diff --git a/include/common/time.h b/include/common/time.h
index 7661aac..7a68a15 100644
--- a/include/common/time.h
+++ b/include/common/time.h
@@ -39,31 +39,31 @@
 /*
  * adds <ms> ms to <from>, set the result to <tv> and returns a pointer <tv>
  */
-struct timeval *tv_delayfrom(struct timeval *tv, struct timeval *from, int ms);
+struct timeval *tv_delayfrom(struct timeval *tv, const struct timeval *from, int ms);
 
 /*
  * compares <tv1> and <tv2> modulo 1ms: returns 0 if equal, -1 if tv1 < tv2, 1 if tv1 > tv2
  * Must not be used when either argument is eternity. Use tv_cmp2_ms() for that.
  */
-int tv_cmp_ms(struct timeval *tv1, struct timeval *tv2);
+int tv_cmp_ms(const struct timeval *tv1, const struct timeval *tv2);
 
 /*
  * compares <tv1> and <tv2> : returns 0 if equal, -1 if tv1 < tv2, 1 if tv1 > tv2,
  * considering that 0 is the eternity.
  */
-int tv_cmp2(struct timeval *tv1, struct timeval *tv2);
+int tv_cmp2(const struct timeval *tv1, const struct timeval *tv2);
 /*
  * compares <tv1> and <tv2> modulo 1 ms: returns 0 if equal, -1 if tv1 < tv2, 1 if tv1 > tv2,
  * considering that 0 is the eternity.
  */
-int tv_cmp2_ms(struct timeval *tv1, struct timeval *tv2);
+int tv_cmp2_ms(const struct timeval *tv1, const struct timeval *tv2);
 
 /*
  * returns the remaining time between tv1=now and event=tv2
  * if tv2 is passed, 0 is returned.
  * Returns TIME_ETERNITY if tv2 is eternity.
  */
-unsigned long tv_remain2(struct timeval *tv1, struct timeval *tv2);
+unsigned long tv_remain2(const struct timeval *tv1, const struct timeval *tv2);
 
 
 /* sets <tv> to the current time */
@@ -78,7 +78,7 @@
  * compares <tv1> and <tv2> : returns 0 if equal, -1 if tv1 < tv2, 1 if tv1 > tv2
  * Must not be used when either argument is eternity. Use tv_cmp2() for that.
  */
-static inline int tv_cmp(struct timeval *tv1, struct timeval *tv2)
+static inline int tv_cmp(const struct timeval *tv1, const struct timeval *tv2)
 {
 	if (tv1->tv_sec < tv2->tv_sec)
 		return -1;
@@ -96,7 +96,7 @@
  * returns the difference, in ms, between tv1 and tv2
  * Must not be used when either argument is eternity.
  */
-static inline unsigned long tv_diff(struct timeval *tv1, struct timeval *tv2)
+static inline unsigned long tv_diff(const struct timeval *tv1, const struct timeval *tv2)
 {
 	unsigned long ret;
   
@@ -113,7 +113,7 @@
  * if tv2 is passed, 0 is returned.
  * Must not be used when either argument is eternity.
  */
-static inline unsigned long tv_remain(struct timeval *tv1, struct timeval *tv2)
+static inline unsigned long tv_remain(const struct timeval *tv1, const struct timeval *tv2)
 {
 	unsigned long ret;
   
@@ -142,7 +142,7 @@
 /*
  * returns 1 if tv is null, else 0
  */
-static inline int tv_iseternity(struct timeval *tv)
+static inline int tv_iseternity(const struct timeval *tv)
 {
 	if (tv->tv_sec == 0 && tv->tv_usec == 0)
 		return 1;
@@ -154,8 +154,9 @@
  * returns the first event between tv1 and tv2 into tvmin.
  * a zero tv is ignored. tvmin is returned.
  */
-static inline struct timeval *tv_min(struct timeval *tvmin,
-				     struct timeval *tv1, struct timeval *tv2)
+static inline const struct timeval *tv_min(struct timeval *tvmin,
+				     const struct timeval *tv1,
+				     const struct timeval *tv2)
 {
 
 	if (tv_cmp2(tv1, tv2) <= 0)