diff --git a/cbits/win_patch.h b/cbits/win_patch.h
new file mode 100644
--- /dev/null
+++ b/cbits/win_patch.h
@@ -0,0 +1,155 @@
+#ifndef UNIX_TIME_WIN_PATCH_H
+#define UNIX_TIME_WIN_PATCH_H
+
+#include "config.h"
+
+#include <sys/cdefs.h>
+
+#include <time.h>
+#include <ctype.h>
+#include <errno.h>
+#include <locale.h>
+#include <stdlib.h>
+#include <string.h>
+#include <pthread.h>
+
+#if defined(_WIN32)
+#include <Windows.h>
+#endif
+
+#if !defined(TM_YEAR_BASE)
+#define TM_YEAR_BASE 1900
+#endif
+
+#if !defined(TM_SUNDAY)
+#define TM_SUNDAY   0
+#endif
+
+#if !defined(TM_MONDAY)
+#define TM_MONDAY   1
+#endif
+
+#if !defined(DAYSPERLYEAR)
+#define DAYSPERLYEAR    366
+#endif
+
+#if !defined(SECSPERMIN)
+#define SECSPERMIN  60
+#endif
+
+#if !defined(MINSPERHOUR)
+#define MINSPERHOUR 60
+#endif
+
+#if !defined(HOURSPERDAY)
+#define HOURSPERDAY 24
+#endif
+
+#if !defined(TM_YEAR_BASE)
+#define TM_YEAR_BASE    1900
+#endif
+
+#if !defined(MONSPERYEAR)
+#define MONSPERYEAR 12
+#endif
+
+#if !defined(DAYSPERWEEK)
+#define DAYSPERWEEK 7
+#endif
+
+#if !defined(DAYSPERNYEAR)
+#define DAYSPERNYEAR    365
+#endif
+
+#ifndef TYPE_BIT
+#define TYPE_BIT(type)  (sizeof (type) * CHAR_BIT)
+#endif /* !defined TYPE_BIT */
+
+#ifndef TYPE_SIGNED
+#define TYPE_SIGNED(type) (((type) -1) < 0)
+#endif /* !defined TYPE_SIGNED */
+
+#ifndef INT_STRLEN_MAXIMUM
+/*
+** 302 / 1000 is log10(2.0) rounded up.
+** Subtract one for the sign bit if the type is signed;
+** add one for integer division truncation;
+** add one more for a minus sign if the type is signed.
+*/
+#define INT_STRLEN_MAXIMUM(type) \
+    ((TYPE_BIT(type) - TYPE_SIGNED(type)) * 302 / 1000 + \
+    1 + TYPE_SIGNED(type))
+#endif /* !defined INT_STRLEN_MAXIMUM */
+
+#define isspace_l _isspace_l
+#define isupper_l _isupper_l
+#define isdigit_l _isdigit_l
+
+#if !HAVE_STRTOL_L
+long strtol_l(const char *nptr, char **endptr, int base, _locale_t locale);
+#endif
+
+#if !HAVE_STRTOLL_L
+long long strtoll_l(const char *nptr, char **endptr, int base, _locale_t locale);
+#endif
+
+#define isleap(y) (((y) % 4) == 0 && (((y) % 100) != 0 || ((y) % 400) == 0))
+
+#ifndef isleap_sum
+/*
+** See tzfile.h for details on isleap_sum.
+*/
+#define isleap_sum(a, b)    isleap((a) % 400 + (b) % 400)
+#endif /* !defined isleap_sum */
+
+int isblank_l( int c, _locale_t _loc);
+
+int strncasecmp_l(const char *s1, const char *s2, int len, _locale_t _loc);
+
+struct tm *gmtime_r(const time_t *_time_t, struct tm *_tm);
+
+struct tm *localtime_r(const time_t *_time_t, struct tm *_tm);
+
+#if HAVE__MKGMTIME
+#define timegm _mkgmtime
+#define HAVE_TIMEGM 1
+#endif
+
+#define fprintf_l(fp, loc, ...) fprintf(fp, ##__VA_ARGS__)
+#define sprintf_l(buf, loc, ...) sprintf(buf, ##__VA_ARGS__)
+
+struct lc_time_T {
+    const char  *mon[12];
+    const char  *month[12];
+    const char  *wday[7];
+    const char  *weekday[7];
+    const char  *X_fmt;
+    const char  *x_fmt;
+    const char  *c_fmt;
+    const char  *am;
+    const char  *pm;
+    const char  *date_fmt;
+    const char  *alt_month[12];
+    const char  *md_order;
+    const char  *ampm_fmt;
+};
+
+extern const struct lc_time_T   _C_time_locale;
+
+int _patch_setenv(const char *var, const char *val, int ovr);
+
+int _patch_unsetenv(const char *name);
+
+size_t _patch_strftime(char * __restrict s, size_t maxsize, const char * __restrict format,
+    const struct tm * __restrict t);
+
+size_t _patch_strftime_l(char * __restrict s, size_t maxsize, const char * __restrict format,
+    const struct tm * __restrict t, _locale_t loc);
+
+char *strptime_l(const char * __restrict buf, const char * __restrict fmt,
+    struct tm * __restrict tm, _locale_t loc);
+
+char *strptime(const char * __restrict buf, const char * __restrict fmt,
+    struct tm * __restrict tm);
+
+#endif // UNIX_TIME_WIN_PATCH_H
diff --git a/unix-time.cabal b/unix-time.cabal
--- a/unix-time.cabal
+++ b/unix-time.cabal
@@ -1,5 +1,5 @@
 Name:                   unix-time
-Version:                0.4.0
+Version:                0.4.1
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3
@@ -31,6 +31,7 @@
     C-Sources:          cbits/strftime.c
                       , cbits/strptime.c
                       , cbits/win_patch.c
+                      , cbits/win_patch.h
   include-dirs:         cbits
 
 Test-Suite doctest