diff --git a/Makefile b/Makefile
index 0aab4000..f2abb399 100644
--- a/Makefile
+++ b/Makefile
@@ -6,7 +6,7 @@ build:
 	cd src; \
 	yacc -d parse.y; \
 	lex scan.l
-	 $(CC) -Wall -o bin/picrin -I./include -lreadline src/main.c src/state.c src/gc.c src/pair.c src/port.c src/symbol.c src/value.c src/y.tab.c src/lex.yy.c src/bool.c src/vm.c src/init.c src/number.c
+	 $(CC) -Wall -o bin/picrin -I./include -lreadline src/main.c src/state.c src/gc.c src/pair.c src/port.c src/symbol.c src/value.c src/y.tab.c src/lex.yy.c src/bool.c src/vm.c src/init.c src/number.c src/time.c
 
 clean:
 	rm -f src/y.tab.c src/y.tab.h src/lex.yy.c
diff --git a/src/init.c b/src/init.c
index ce4defff..2c330247 100644
--- a/src/init.c
+++ b/src/init.c
@@ -2,6 +2,7 @@
 
 void pic_init_port(pic_state *);
 void pic_init_number(pic_state *);
+void pic_init_time(pic_state *);
 
 #define DONE pic_gc_arena_restore(pic, ai);
 
@@ -13,4 +14,5 @@ pic_init_core(pic_state *pic)
   ai = pic_gc_arena_preserve(pic);
   pic_init_port(pic); DONE;
   pic_init_number(pic); DONE;
+  pic_init_time(pic); DONE;
 }
diff --git a/src/number.c b/src/number.c
index f865ba7a..084637d4 100644
--- a/src/number.c
+++ b/src/number.c
@@ -1,7 +1,6 @@
 #include <math.h>
 
 #include "picrin.h"
-#include "picrin/value.h"
 
 static pic_value
 pic_number_lt(pic_state *pic)
diff --git a/src/port.c b/src/port.c
index db278eb5..bf502534 100644
--- a/src/port.c
+++ b/src/port.c
@@ -29,7 +29,7 @@ write(pic_state *pic, pic_value obj)
     printf("%s", pic_symbol_ptr(obj)->name);
     break;
   case PIC_TT_FLOAT:
-    printf("%g", pic_float(obj));
+    printf("%.10g", pic_float(obj));
     break;
   case PIC_TT_UNDEF:
     printf("#<undef>");
diff --git a/src/time.c b/src/time.c
new file mode 100644
index 00000000..3de5c44b
--- /dev/null
+++ b/src/time.c
@@ -0,0 +1,44 @@
+#include <time.h>
+#include <stdio.h>
+
+#include "picrin.h"
+
+#define UTC_TAI_DIFF 35
+
+static pic_value
+pic_current_second(pic_state *pic)
+{
+  time_t t;
+
+  pic_get_args(pic, "");
+
+  time(&t);
+  return pic_float_value((double)t + UTC_TAI_DIFF);
+}
+
+static pic_value
+pic_current_jiffy(pic_state *pic)
+{
+  clock_t c;
+
+  pic_get_args(pic, "");
+
+  c = clock();
+  return pic_float_value((double)c);
+}
+
+static pic_value
+pic_jiffies_per_second(pic_state *pic)
+{
+  pic_get_args(pic, "");
+
+  return pic_float_value((double)CLOCKS_PER_SEC);
+}
+
+void
+pic_init_time(pic_state *pic)
+{
+  pic_defun(pic, "current-second", pic_current_second);
+  pic_defun(pic, "current-jiffy", pic_current_jiffy);
+  pic_defun(pic, "jiffies-per-second", pic_jiffies_per_second);
+}