diff --git a/include/mbedtls/check_config.h b/include/mbedtls/check_config.h
index d3c9a9f113..18e6b5677a 100644
--- a/include/mbedtls/check_config.h
+++ b/include/mbedtls/check_config.h
@@ -454,6 +454,12 @@
 #error "MBEDTLS_PLATFORM_MS_TIME_TYPE_MACRO defined, but not all prerequisites"
 #endif
 
+#if defined(MBEDTLS_PLATFORM_MS_TIME_ALT)   && \
+    ( !defined(MBEDTLS_PLATFORM_C)          || \
+        !defined(MBEDTLS_HAVE_TIME) )
+#error "MBEDTLS_PLATFORM_MS_TIME_ALT defined, but not all prerequisites"
+#endif
+
 #if defined(MBEDTLS_PLATFORM_TIME_TYPE_MACRO) &&\
     ( !defined(MBEDTLS_PLATFORM_C) ||\
         !defined(MBEDTLS_HAVE_TIME) )
diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index 34fdfccd24..cfde4b7d03 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -234,6 +234,7 @@
 //#define MBEDTLS_PLATFORM_VSNPRINTF_ALT
 //#define MBEDTLS_PLATFORM_NV_SEED_ALT
 //#define MBEDTLS_PLATFORM_SETUP_TEARDOWN_ALT
+//#define MBEDTLS_PLATFORM_MS_TIME_ALT
 
 /**
  * \def MBEDTLS_DEPRECATED_WARNING
diff --git a/include/mbedtls/platform_time.h b/include/mbedtls/platform_time.h
index e6f7e23bf4..11618072f1 100644
--- a/include/mbedtls/platform_time.h
+++ b/include/mbedtls/platform_time.h
@@ -45,6 +45,16 @@ typedef MBEDTLS_PLATFORM_MS_TIME_TYPE_MACRO mbedtls_ms_time_t;
 typedef signed long long mbedtls_ms_time_t;
 #endif /* MBEDTLS_PLATFORM_MS_TIME_TYPE_MACRO */
 
+/**
+ * \brief Get time in milliseconds.
+ *
+ * \return Current time in milliseconds
+ *
+ * \note If MBEDTLS_PLATFORM_MS_TIME_ALT defined, users can provide their own
+ *       implementation.
+ */
+mbedtls_ms_time_t mbedtls_ms_time(void);
+
 /*
  * The function pointers for time
  */
diff --git a/library/platform_util.c b/library/platform_util.c
index f935b900e8..1f60404fd6 100644
--- a/library/platform_util.c
+++ b/library/platform_util.c
@@ -165,3 +165,43 @@ extern inline void mbedtls_put_unaligned_uint32(void *p, uint32_t x);
 extern inline uint64_t mbedtls_get_unaligned_uint64(const void *p);
 
 extern inline void mbedtls_put_unaligned_uint64(void *p, uint64_t x);
+
+#if defined(MBEDTLS_HAVE_TIME) && !defined(MBEDTLS_PLATFORM_MS_TIME_ALT)
+
+#include <time.h>
+#if !defined(_WIN32) && (defined(unix) || \
+    defined(__unix) || defined(__unix__) || (defined(__APPLE__) && \
+    defined(__MACH__)))
+#include <unistd.h>
+#endif /* !_WIN32 && (unix || __unix || __unix__ ||
+        * (__APPLE__ && __MACH__)) */
+#if (defined(_POSIX_VERSION) && _POSIX_VERSION >= 199309L)
+mbedtls_ms_time_t mbedtls_ms_time(void)
+{
+    int ret;
+    struct timespec tv;
+    mbedtls_ms_time_t current_ms;
+
+    ret = clock_gettime(CLOCK_REALTIME, &tv);
+    if (ret) {
+        return 0;
+    }
+
+    current_ms = tv.tv_sec;
+
+    return current_ms*1000 + tv.tv_nsec / 1000000;
+}
+#elif defined(_WIN32) || defined(WIN32) || defined(__CYGWIN__) || \
+    defined(__MINGW32__) || defined(_WIN64)
+#include <windows.h>
+mbedtls_ms_time_t mbedtls_ms_time(void)
+{
+    SYSTEMTIME st;
+
+    GetSystemTime(&st);
+    return time(NULL)*1000LL + st.wMilliseconds;
+}
+#else
+#error "No mbedtls_ms_time available"
+#endif
+#endif /* MBEDTLS_HAVE_TIME && !MBEDTLS_PLATFORM_MS_TIME_ALT */
diff --git a/scripts/config.py b/scripts/config.py
index a53c470f07..06fc3fafbb 100755
--- a/scripts/config.py
+++ b/scripts/config.py
@@ -229,7 +229,7 @@ def is_seamless_alt(name):
     Exclude alternative implementations of library functions since they require
     an implementation of the relevant functions and an xxx_alt.h header.
     """
-    if name == 'MBEDTLS_PLATFORM_SETUP_TEARDOWN_ALT':
+    if name in ('MBEDTLS_PLATFORM_SETUP_TEARDOWN_ALT', 'MBEDTLS_PLATFORM_MS_TIME_ALT'):
         # Similar to non-platform xxx_ALT, requires platform_alt.h
         return False
     return name.startswith('MBEDTLS_PLATFORM_')