diff --git a/bits/typesizes.h b/bits/typesizes.h
index 85eacf2518..0b6a19c230 100644
--- a/bits/typesizes.h
+++ b/bits/typesizes.h
@@ -48,6 +48,7 @@
 #define	__ID_T_TYPE		__U32_TYPE
 #define __CLOCK_T_TYPE		__SLONGWORD_TYPE
 #define __TIME_T_TYPE		__SLONGWORD_TYPE
+#define __TIME64_T_TYPE		__SQUAD_TYPE
 #define __USECONDS_T_TYPE	__U32_TYPE
 #define __SUSECONDS_T_TYPE	__SLONGWORD_TYPE
 #define __DADDR_T_TYPE		__S32_TYPE
diff --git a/include/time.h b/include/time.h
index 23d2580528..93638aa215 100644
--- a/include/time.h
+++ b/include/time.h
@@ -3,6 +3,7 @@
 
 #ifndef _ISOMAC
 # include <bits/types/locale_t.h>
+# include <stdbool.h>
 
 extern __typeof (strftime_l) __strftime_l;
 libc_hidden_proto (__strftime_l)
@@ -101,10 +102,16 @@ extern char * __strptime_internal (const char *rp, const char *fmt,
 
 extern double __difftime (time_t time1, time_t time0);
 
-
 /* Use in the clock_* functions.  Size of the field representing the
    actual clock ID.  */
 #define CLOCK_IDFIELD_SIZE	3
 
+/* check whether a time64_t value fits in a time_t */
+static inline bool
+fits_in_time_t (__time64_t t)
+{
+  return t == (time_t) t;
+}
+
 #endif
 #endif
diff --git a/posix/bits/types.h b/posix/bits/types.h
index 5e22ce41bf..4c6553a266 100644
--- a/posix/bits/types.h
+++ b/posix/bits/types.h
@@ -155,7 +155,8 @@ __STD_TYPE __CLOCK_T_TYPE __clock_t;	/* Type of CPU usage counts.  */
 __STD_TYPE __RLIM_T_TYPE __rlim_t;	/* Type for resource measurement.  */
 __STD_TYPE __RLIM64_T_TYPE __rlim64_t;	/* Type for resource measurement (LFS).  */
 __STD_TYPE __ID_T_TYPE __id_t;		/* General type for IDs.  */
-__STD_TYPE __TIME_T_TYPE __time_t;	/* Seconds since the Epoch.  */
+__STD_TYPE __TIME_T_TYPE __time_t;	/* Seconds since the Epoch, Y2038-unsafe.  */
+__STD_TYPE __TIME64_T_TYPE __time64_t;	/* Seconds since the Epoch, Y2038-safe.  */
 __STD_TYPE __USECONDS_T_TYPE __useconds_t; /* Count of microseconds.  */
 __STD_TYPE __SUSECONDS_T_TYPE __suseconds_t; /* Signed count of microseconds.  */
 
diff --git a/sysdeps/mach/hurd/bits/typesizes.h b/sysdeps/mach/hurd/bits/typesizes.h
index d3026ba66e..c9dbe2bf33 100644
--- a/sysdeps/mach/hurd/bits/typesizes.h
+++ b/sysdeps/mach/hurd/bits/typesizes.h
@@ -48,6 +48,7 @@
 #define	__ID_T_TYPE		__U32_TYPE
 #define __CLOCK_T_TYPE		__SLONGWORD_TYPE
 #define __TIME_T_TYPE		__SLONGWORD_TYPE
+#define __TIME64_T_TYPE		__SQUAD_TYPE
 #define __USECONDS_T_TYPE	__U32_TYPE
 #define __SUSECONDS_T_TYPE	__SLONGWORD_TYPE
 #define __DADDR_T_TYPE		__S32_TYPE
diff --git a/sysdeps/unix/sysv/linux/alpha/bits/typesizes.h b/sysdeps/unix/sysv/linux/alpha/bits/typesizes.h
index d9a0b0467c..47b1e36165 100644
--- a/sysdeps/unix/sysv/linux/alpha/bits/typesizes.h
+++ b/sysdeps/unix/sysv/linux/alpha/bits/typesizes.h
@@ -47,6 +47,7 @@
 #define	__ID_T_TYPE		__U32_TYPE
 #define __CLOCK_T_TYPE		__SLONGWORD_TYPE
 #define __TIME_T_TYPE		__SLONGWORD_TYPE
+#define __TIME64_T_TYPE		__SQUAD_TYPE
 #define __USECONDS_T_TYPE	__U32_TYPE
 #define __SUSECONDS_T_TYPE	__S64_TYPE
 #define __DADDR_T_TYPE		__S32_TYPE
diff --git a/sysdeps/unix/sysv/linux/generic/bits/typesizes.h b/sysdeps/unix/sysv/linux/generic/bits/typesizes.h
index a2cb3433bf..db03b1ae8b 100644
--- a/sysdeps/unix/sysv/linux/generic/bits/typesizes.h
+++ b/sysdeps/unix/sysv/linux/generic/bits/typesizes.h
@@ -49,6 +49,7 @@
 #define	__ID_T_TYPE		__U32_TYPE
 #define __CLOCK_T_TYPE		__SLONGWORD_TYPE
 #define __TIME_T_TYPE		__SLONGWORD_TYPE
+#define __TIME64_T_TYPE		__SQUAD_TYPE
 #define __USECONDS_T_TYPE	__U32_TYPE
 #define __SUSECONDS_T_TYPE	__SLONGWORD_TYPE
 #define __DADDR_T_TYPE		__S32_TYPE
diff --git a/sysdeps/unix/sysv/linux/s390/bits/typesizes.h b/sysdeps/unix/sysv/linux/s390/bits/typesizes.h
index fdaa421958..138c6d6d10 100644
--- a/sysdeps/unix/sysv/linux/s390/bits/typesizes.h
+++ b/sysdeps/unix/sysv/linux/s390/bits/typesizes.h
@@ -48,6 +48,7 @@
 #define	__ID_T_TYPE		__U32_TYPE
 #define __CLOCK_T_TYPE		__SLONGWORD_TYPE
 #define __TIME_T_TYPE		__SLONGWORD_TYPE
+#define __TIME64_T_TYPE		__SQUAD_TYPE
 #define __USECONDS_T_TYPE	__U32_TYPE
 #define __SUSECONDS_T_TYPE	__SLONGWORD_TYPE
 #define __DADDR_T_TYPE		__S32_TYPE
diff --git a/sysdeps/unix/sysv/linux/sparc/bits/typesizes.h b/sysdeps/unix/sysv/linux/sparc/bits/typesizes.h
index b59f2ced75..5d6fb00a93 100644
--- a/sysdeps/unix/sysv/linux/sparc/bits/typesizes.h
+++ b/sysdeps/unix/sysv/linux/sparc/bits/typesizes.h
@@ -48,6 +48,7 @@
 #define	__ID_T_TYPE		__U32_TYPE
 #define __CLOCK_T_TYPE		__SLONGWORD_TYPE
 #define __TIME_T_TYPE		__SLONGWORD_TYPE
+#define __TIME64_T_TYPE		__SQUAD_TYPE
 #define __USECONDS_T_TYPE	__U32_TYPE
 #define __SUSECONDS_T_TYPE	__S32_TYPE
 #define __DADDR_T_TYPE		__S32_TYPE
diff --git a/sysdeps/unix/sysv/linux/x86/bits/typesizes.h b/sysdeps/unix/sysv/linux/x86/bits/typesizes.h
index e6f7481a19..f5d792d8f3 100644
--- a/sysdeps/unix/sysv/linux/x86/bits/typesizes.h
+++ b/sysdeps/unix/sysv/linux/x86/bits/typesizes.h
@@ -62,6 +62,7 @@
 #define __ID_T_TYPE		__U32_TYPE
 #define __CLOCK_T_TYPE		__SYSCALL_SLONG_TYPE
 #define __TIME_T_TYPE		__SYSCALL_SLONG_TYPE
+#define __TIME64_T_TYPE		__SQUAD_TYPE
 #define __USECONDS_T_TYPE	__U32_TYPE
 #define __SUSECONDS_T_TYPE	__SYSCALL_SLONG_TYPE
 #define __DADDR_T_TYPE		__S32_TYPE
