diff --git a/c/space-age/GNUmakefile b/c/space-age/GNUmakefile
new file mode 100644
index 0000000..ec085d0
--- /dev/null
+++ b/c/space-age/GNUmakefile
@@ -0,0 +1,51 @@
+# The original 'makefile' has a flaw:
+# 1) it overrides CFLAGS
+# 2) it does not pass extra "FLAGS" to $(CC) that could come from environment
+#
+# It means :
+# - we need to edit 'makefile' for different builds (DEBUG, etc...), which is
+#   not practical at all.
+# - Also, it does not allow to run all tests without editing the test source
+#   code.
+#
+# To use this makefile (GNU make only):
+#   "make": build with all predefined tests (without editing test source code)
+#   "make debugall": build with all predefined tests and debug code
+#   "make mem": perform memcheck with all tests enabled
+#   "make unit": build standalone (unit) test
+#   "make debug": build standalone test with debugging code
+#
+# Original 'makefile' targets can be used (test, memcheck, clean, ...)
+
+.PHONY: default all mem unit debug std debugtest
+
+default: all
+
+# default is to build with all predefined tests
+BUILD := teststall
+
+include makefile
+
+all: CFLAGS+=-DTESTALL
+all: clean test
+
+debugall: CFLAGS+=-DDEBUG
+debugall: all
+
+debugtest: CFLAGS+=-DDEBUG
+debugtest: test
+
+mem: CFLAGS+=-DTESTALL
+mem: clean memcheck
+
+unit: CFLAGS+=-DUNIT_TEST
+unit: clean std
+
+debug: CFLAGS+=-DUNIT_TEST -DDEBUG
+debug: clean std
+
+debugtest: CFLAGS+=-DDEBUG
+debugtest: test
+
+std: src/*.c src/*.h
+	$(CC) $(CFLAGS) src/*.c -o test.out
diff --git a/c/space-age/README.md b/c/space-age/README.md
new file mode 100644
index 0000000..da40d13
--- /dev/null
+++ b/c/space-age/README.md
@@ -0,0 +1,56 @@
+# Space Age
+
+Given an age in seconds, calculate how old someone would be on:
+
+   - Mercury: orbital period 0.2408467 Earth years
+   - Venus: orbital period 0.61519726 Earth years
+   - Earth: orbital period 1.0 Earth years, 365.25 Earth days, or 31557600 seconds
+   - Mars: orbital period 1.8808158 Earth years
+   - Jupiter: orbital period 11.862615 Earth years
+   - Saturn: orbital period 29.447498 Earth years
+   - Uranus: orbital period 84.016846 Earth years
+   - Neptune: orbital period 164.79132 Earth years
+
+So if you were told someone were 1,000,000,000 seconds old, you should
+be able to say that they're 31.69 Earth-years old.
+
+If you're wondering why Pluto didn't make the cut, go watch [this
+youtube video](http://www.youtube.com/watch?v=Z_2gbGXzFbs).
+
+## Getting Started
+
+Make sure you have read the "Guides" section of the
+[C track][c-track] on the Exercism site. This covers
+the basic information on setting up the development environment expected
+by the exercises.
+
+## Passing the Tests
+
+Get the first test compiling, linking and passing by following the [three
+rules of test-driven development][3-tdd-rules].
+
+The included makefile can be used to create and run the tests using the `test`
+task.
+
+    make test
+
+Create just the functions you need to satisfy any compiler errors and get the
+test to fail. Then write just enough code to get the test to pass. Once you've
+done that, move onto the next test.
+
+As you progress through the tests, take the time to refactor your
+implementation for readability and expressiveness and then go on to the next
+test.
+
+Try to use standard C99 facilities in preference to writing your own
+low-level algorithms or facilities by hand.
+
+## Source
+
+Partially inspired by Chapter 1 in Chris Pine's online Learn to Program tutorial. [http://pine.fm/LearnToProgram/?Chapter=01](http://pine.fm/LearnToProgram/?Chapter=01)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
+
+[c-track]: https://exercism.io/my/tracks/c
+[3-tdd-rules]: http://butunclebob.com/ArticleS.UncleBob.TheThreeRulesOfTdd
diff --git a/c/space-age/makefile b/c/space-age/makefile
new file mode 100644
index 0000000..f34535a
--- /dev/null
+++ b/c/space-age/makefile
@@ -0,0 +1,37 @@
+### If you wish to use extra libraries (math.h for instance),
+### add their flags here (-lm in our case) in the "LIBS" variable.
+
+LIBS = -lm
+
+###
+CFLAGS  = -std=c99
+CFLAGS += -g
+CFLAGS += -Wall
+CFLAGS += -Wextra
+CFLAGS += -pedantic
+CFLAGS += -Werror
+CFLAGS += -Wmissing-declarations
+CFLAGS += -DUNITY_SUPPORT_64
+
+ASANFLAGS  = -fsanitize=address
+ASANFLAGS += -fno-common
+ASANFLAGS += -fno-omit-frame-pointer
+
+.PHONY: test
+test: tests.out
+	@./tests.out
+
+.PHONY: memcheck
+memcheck: test/*.c src/*.c src/*.h
+	@echo Compiling $@
+	@$(CC) $(ASANFLAGS) $(CFLAGS) src/*.c test/vendor/unity.c test/*.c -o memcheck.out $(LIBS)
+	@./memcheck.out
+	@echo "Memory check passed"
+
+.PHONY: clean
+clean:
+	rm -rf *.o *.out *.out.dSYM
+
+tests.out: test/*.c src/*.c src/*.h
+	@echo Compiling $@
+	@$(CC) $(CFLAGS) src/*.c test/vendor/unity.c test/*.c -o tests.out $(LIBS)
diff --git a/c/space-age/src/space_age.c b/c/space-age/src/space_age.c
new file mode 100644
index 0000000..875921e
--- /dev/null
+++ b/c/space-age/src/space_age.c
@@ -0,0 +1,41 @@
+#include <time.h>
+#include "space_age.h"
+
+/* See GNUmakefile below for explanation
+ * https://github.com/braoult/exercism/blob/master/c/templates/GNUmakefile
+ */
+#if defined UNIT_TEST || defined DEBUG
+#include <stdio.h>
+#include <stdlib.h>
+#endif
+
+static float relative[] = {
+    0.2408467,
+    0.61519726,
+    1.0,
+    1.8808158,
+    11.862615,
+    29.447498,
+    84.016846,
+    164.79132
+};
+#define EARTH_SECS 31557600
+
+float age(planet_t p, int64_t s)
+{
+    return s/EARTH_SECS/relative[p];
+}
+
+#ifdef UNIT_TEST
+int main(int ac, char **av)
+{
+    int arg=1, i;
+    float f;
+
+    for (; arg<ac-1; ++arg, ++arg) {
+        i=atoi(av[arg]);
+        f=atof(av[arg+1]);
+        printf("age(%d, %f)=%f\n", i, f, age(i, f));
+    }
+}
+#endif
diff --git a/c/space-age/src/space_age.h b/c/space-age/src/space_age.h
new file mode 100644
index 0000000..e2ff420
--- /dev/null
+++ b/c/space-age/src/space_age.h
@@ -0,0 +1,27 @@
+#ifndef SPACE_AGE_H
+#define SPACE_AGE_H
+
+#include <stdint.h>
+
+typedef enum planet {
+   MERCURY = 0,
+   VENUS,
+   EARTH,
+   MARS,
+   JUPITER,
+   SATURN,
+   URANUS,
+   NEPTUNE,
+} planet_t;
+
+float age(planet_t planet, int64_t seconds);
+
+/* See GNUmakefile below for explanation
+ * https://github.com/braoult/exercism/blob/master/c/templates/GNUmakefile
+ */
+#ifdef  TESTALL
+#undef  TEST_IGNORE
+#define TEST_IGNORE() {}
+#endif
+
+#endif
diff --git a/c/templates/ex.c b/c/templates/ex.c
index 477f76e..3bed2fd 100644
--- a/c/templates/ex.c
+++ b/c/templates/ex.c
@@ -1,5 +1,5 @@
-/* See GNUmakefile in following link for explanation
- * https://exercism.io/my/solutions/103b2f7d92db42309c1988030f5202c7
+/* See GNUmakefile below explanation
+ * https://github.com/braoult/exercism/blob/master/c/templates/GNUmakefile
  */
 #if defined UNIT_TEST || defined DEBUG
 #include <stdio.h>
diff --git a/c/templates/ex.h b/c/templates/ex.h
index 500d3e6..63a0c42 100644
--- a/c/templates/ex.h
+++ b/c/templates/ex.h
@@ -1,5 +1,5 @@
-/* See GNUmakefile in following link for explanation
- * https://exercism.io/my/solutions/103b2f7d92db42309c1988030f5202c7
+/* See GNUmakefile below for explanation
+ * https://github.com/braoult/exercism/blob/master/c/templates/GNUmakefile
  */
 #ifdef  TESTALL
 #undef  TEST_IGNORE