diff --git a/Makefile b/Makefile
index 6edc73cc..0e56af89 100644
--- a/Makefile
+++ b/Makefile
@@ -353,6 +353,7 @@ GCC_DEBUG_FLAGS = -DGCC_LINT -g3 -O3 -fno-common \
 # functions to be added to the time conversion library.
 # "offtime" is like "gmtime" except that it accepts a second (long) argument
 # that gives an offset to add to the time_t when converting it.
+# "offtime_r" is to "offtime" what "gmtime_r" is to "gmtime".
 # "timelocal" is equivalent to "mktime".
 # "timeoff" is like "timegm" except that it accepts a second (long) argument
 # that gives an offset to use when converting to a time_t.
diff --git a/localtime.c b/localtime.c
index 818d58f8..585dfe13 100644
--- a/localtime.c
+++ b/localtime.c
@@ -1704,14 +1704,19 @@ gmtime(const time_t *timep)
 #if STD_INSPIRED
 
 struct tm *
-offtime(const time_t *timep, long offset)
+offtime_r(time_t const *restrict timep, long offset, struct tm *restrict tmp)
 {
   gmtcheck();
+  return gmtsub(gmtptr, timep, offset, tmp);
+}
 
+struct tm *
+offtime(const time_t *timep, long offset)
+{
 #if !SUPPORT_C89
   static struct tm tm;
 #endif
-  return gmtsub(gmtptr, timep, offset, &tm);
+  return offtime_r(timep, offset, &tm);
 }
 
 #endif
diff --git a/private.h b/private.h
index 838ab2b2..5a1dbb02 100644
--- a/private.h
+++ b/private.h
@@ -626,6 +626,8 @@ typedef time_tz tz_time_t;
 # define mktime_z tz_mktime_z
 # undef  offtime
 # define offtime tz_offtime
+# undef  offtime_r
+# define offtime_r tz_offtime_r
 # undef  posix2time
 # define posix2time tz_posix2time
 # undef  posix2time_z
@@ -750,6 +752,9 @@ extern long altzone;
 # if TZ_TIME_T || !defined offtime
 struct tm *offtime(time_t const *, long);
 # endif
+# if TZ_TIME_T || !defined offtime_r
+struct tm *offtime_r(time_t const *, long, struct tm *);
+# endif
 # if TZ_TIME_T || !defined timelocal
 time_t timelocal(struct tm *);
 # endif