diff --git a/ChangeLog b/ChangeLog
index 8c26806..49dc84e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,21 @@
 2019-04-06  Mike Crowe  <mac@mcrowe.com>
 
+	* support/timespec.h: New file. Provide timespec helper functions
+	along with macros in the style of those in check.h.
+
+	* support/timespec.c: New file. Implement check functions declared
+	in support/timespec.h.
+
+	* support/timespec-add.c: New file from gnulib containing
+	timespec_add implementation that handles overflow.
+
+	* support/timespec-sub.c: New file from gnulib containing
+	timespec_sub implementation that handles overflow.
+
+	* support/README: Mention timespec.h.
+
+2019-04-06  Mike Crowe  <mac@mcrowe.com>
+
 	* support/xclock_gettime.c (xclock_gettime): New file. Provide
 	clock_gettime wrapper for use in tests that fails the test rather
 	than returning failure.
diff --git a/support/Makefile b/support/Makefile
index 1d37f70..94a1416 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -70,6 +70,9 @@ libsupport-routines = \
   support_test_main \
   support_test_verify_impl \
   temp_file \
+  timespec \
+  timespec-add \
+  timespec-sub \
   write_message \
   xaccept \
   xaccept4 \
diff --git a/support/README b/support/README
index d82f472..e33067e 100644
--- a/support/README
+++ b/support/README
@@ -28,3 +28,8 @@ header files provide related declarations:
 * check.h
 * temp_file.h
 * test-driver.h
+
+For tests that make use of struct timespec, the following header file
+contains additional macros and helper functions:
+
+* timespec.h
diff --git a/support/timespec-add.c b/support/timespec-add.c
new file mode 100644
index 0000000..523eac8
--- /dev/null
+++ b/support/timespec-add.c
@@ -0,0 +1,75 @@
+/* Add two struct timespec values.
+
+   Copyright (C) 2011-2019 Free Software Foundation, Inc.
+
+   This file is part of the GNU C Library, although it originally came
+   from gnulib.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* Written by Paul Eggert.  */
+
+/* Return the sum of two timespec values A and B.  On overflow, return
+   an extremal value.  This assumes 0 <= tv_nsec < TIMESPEC_HZ.  */
+
+#include <config.h>
+#include "timespec.h"
+
+#include "intprops.h"
+
+struct timespec
+timespec_add (struct timespec a, struct timespec b)
+{
+  time_t rs = a.tv_sec;
+  time_t bs = b.tv_sec;
+  int ns = a.tv_nsec + b.tv_nsec;
+  int nsd = ns - TIMESPEC_HZ;
+  int rns = ns;
+  time_t tmin = TYPE_MINIMUM (time_t);
+  time_t tmax = TYPE_MAXIMUM (time_t);
+
+  if (0 <= nsd)
+    {
+      rns = nsd;
+      if (bs < tmax)
+        bs++;
+      else if (rs < 0)
+        rs++;
+      else
+        goto high_overflow;
+    }
+
+  /* INT_ADD_WRAPV is not appropriate since time_t might be unsigned.
+     In theory time_t might be narrower than int, so plain
+     INT_ADD_OVERFLOW does not suffice.  */
+  if (! INT_ADD_OVERFLOW (rs, bs) && tmin <= rs + bs && rs + bs <= tmax)
+    rs += bs;
+  else
+    {
+      if (rs < 0)
+        {
+          rs = tmin;
+          rns = 0;
+        }
+      else
+        {
+        high_overflow:
+          rs = tmax;
+          rns = TIMESPEC_HZ - 1;
+        }
+    }
+
+  return make_timespec (rs, rns);
+}
diff --git a/support/timespec-sub.c b/support/timespec-sub.c
new file mode 100644
index 0000000..7e67e87
--- /dev/null
+++ b/support/timespec-sub.c
@@ -0,0 +1,75 @@
+/* Subtract two struct timespec values.
+
+   Copyright (C) 2011-2019 Free Software Foundation, Inc.
+
+   This file is part of the GNU C Library, although it originally came
+   from gnulib.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* Written by Paul Eggert.  */
+
+/* Return the difference between two timespec values A and B.  On
+   overflow, return an extremal value.  This assumes 0 <= tv_nsec <
+   TIMESPEC_HZ.  */
+
+#include <config.h>
+#include "timespec.h"
+
+#include "intprops.h"
+
+struct timespec
+timespec_sub (struct timespec a, struct timespec b)
+{
+  time_t rs = a.tv_sec;
+  time_t bs = b.tv_sec;
+  int ns = a.tv_nsec - b.tv_nsec;
+  int rns = ns;
+  time_t tmin = TYPE_MINIMUM (time_t);
+  time_t tmax = TYPE_MAXIMUM (time_t);
+
+  if (ns < 0)
+    {
+      rns = ns + TIMESPEC_HZ;
+      if (bs < tmax)
+        bs++;
+      else if (- TYPE_SIGNED (time_t) < rs)
+        rs--;
+      else
+        goto low_overflow;
+    }
+
+  /* INT_SUBTRACT_WRAPV is not appropriate since time_t might be unsigned.
+     In theory time_t might be narrower than int, so plain
+     INT_SUBTRACT_OVERFLOW does not suffice.  */
+  if (! INT_SUBTRACT_OVERFLOW (rs, bs) && tmin <= rs - bs && rs - bs <= tmax)
+    rs -= bs;
+  else
+    {
+      if (rs < 0)
+        {
+        low_overflow:
+          rs = tmin;
+          rns = 0;
+        }
+      else
+        {
+          rs = tmax;
+          rns = TIMESPEC_HZ - 1;
+        }
+    }
+
+  return make_timespec (rs, rns);
+}
diff --git a/support/timespec.c b/support/timespec.c
new file mode 100644
index 0000000..c34fe73
--- /dev/null
+++ b/support/timespec.c
@@ -0,0 +1,63 @@
+/* Support code for timespec checks.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/timespec.h>
+#include <errno.h>
+#include <stdio.h>
+
+void
+test_timespec_before_impl (const char *file, int line,
+			   const struct timespec left,
+			   const struct timespec right)
+{
+  if (left.tv_sec > right.tv_sec
+      || (left.tv_sec == right.tv_sec
+	  && left.tv_nsec > right.tv_nsec)) {
+    const int saved_errno = errno;
+    support_record_failure ();
+    const struct timespec diff = timespec_sub (left, right);
+    printf ("%s:%d: %ld.%09lds not before %ld.%09lds "
+	    "(difference %ld.%09lds)n",
+	    file, line,
+	    left.tv_sec, left.tv_nsec,
+	    right.tv_sec, right.tv_nsec,
+	    diff.tv_sec, diff.tv_nsec);
+    errno = saved_errno;
+  }
+}
+
+void
+test_timespec_equal_or_after_impl (const char *file, int line,
+				   const struct timespec left,
+				   const struct timespec right)
+{
+  if (left.tv_sec < right.tv_sec
+      || (left.tv_sec == right.tv_sec
+	  && left.tv_nsec < right.tv_nsec)) {
+    const int saved_errno = errno;
+    support_record_failure ();
+    const struct timespec diff = timespec_sub (right, left);
+    printf ("%s:%d: %ld.%09lds not after %ld.%09lds "
+	    "(difference %ld.%09lds)n",
+	    file, line,
+	    left.tv_sec, left.tv_nsec,
+	    right.tv_sec, right.tv_nsec,
+	    diff.tv_sec, diff.tv_nsec);
+    errno = saved_errno;
+  }
+}
diff --git a/support/timespec.h b/support/timespec.h
new file mode 100644
index 0000000..4a8b341
--- /dev/null
+++ b/support/timespec.h
@@ -0,0 +1,79 @@
+/* Useful functions for tests that use struct timespec.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_TIMESPEC_H
+#define SUPPORT_TIMESPEC_H
+
+#include <stdio.h>
+#include <time.h>
+#include <support/check.h>
+#include <support/xtime.h>
+
+struct timespec timespec_add (struct timespec, struct timespec)
+  __attribute__((const));
+struct timespec timespec_sub (struct timespec, struct timespec)
+  __attribute__((const));
+
+static inline struct timespec
+make_timespec (time_t s, long int ns)
+{
+  struct timespec r;
+  r.tv_sec = s;
+  r.tv_nsec = ns;
+  return r;
+}
+
+enum { TIMESPEC_HZ = 1000000000 };
+
+void test_timespec_before_impl (const char *file, int line,
+                                const struct timespec left,
+                                const struct timespec right);
+
+void test_timespec_equal_or_after_impl (const char *file, int line,
+                                        const struct timespec left,
+                                        const struct timespec right);
+
+/* Check that the timespec on the left represents a time before the
+   time on the right. */
+#define TEST_TIMESPEC_BEFORE(left, right)                               \
+  test_timespec_before_impl (__FILE__, __LINE__, (left), (right))
+
+#define TEST_TIMESPEC_BEFORE_NOW(left, clockid)                 \
+  ({                                                            \
+    struct timespec now;                                        \
+    const int saved_errno = errno;                              \
+    xclock_gettime ((clockid), &now);                           \
+    TEST_TIMESPEC_BEFORE ((left), now);                         \
+    errno = saved_errno;                                        \
+  })
+
+/* Check that the timespec on the left represents a after before the
+   time on the right. */
+#define TEST_TIMESPEC_EQUAL_OR_AFTER(left, right)                       \
+  test_timespec_equal_or_after_impl (__FILE__, __LINE__, left, right)
+
+#define TEST_TIMESPEC_NOW_OR_AFTER(clockid, right)              \
+  ({                                                            \
+    struct timespec now;                                        \
+    const int saved_errno = errno;                              \
+    xclock_gettime ((clockid), &now);                           \
+    TEST_TIMESPEC_EQUAL_OR_AFTER (now, (right));                \
+    errno = saved_errno;                                        \
+  })
+
+#endif /* SUPPORT_TIMESPEC_H */
