diff --git a/include/pybind11/chrono.h b/include/pybind11/chrono.h
index 007cc17b4..460a28fa5 100644
--- a/include/pybind11/chrono.h
+++ b/include/pybind11/chrono.h
@@ -17,8 +17,6 @@
 #include <ctime>
 #include <mutex>
 
-#include <time.h>
-
 #include <datetime.h>
 
 // Backport the PyDateTime_DELTA functions from Python3.3 if required
@@ -108,7 +106,7 @@ inline std::tm *localtime_thread_safe(const std::time_t *time, std::tm *buf) {
 #else
     static std::mutex mtx;
     std::lock_guard<std::mutex> lock(mtx);
-    std::tm *tm_ptr = localtime(time);
+    std::tm *tm_ptr = std::localtime(time);
     if (tm_ptr != nullptr) {
         *buf = *tm_ptr;
     }
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index b9376b4c0..cc1e40ce7 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -624,9 +624,9 @@ inline PyObject* make_new_python_type(const type_record &rec) {
     if (rec.doc && options::show_user_defined_docstrings()) {
         /* Allocate memory for docstring (using PyObject_MALLOC, since
            Python will free this later on) */
-        size_t size = strlen(rec.doc) + 1;
+        size_t size = std::strlen(rec.doc) + 1;
         tp_doc = (char *) PyObject_MALLOC(size);
-        memcpy((void *) tp_doc, rec.doc, size);
+        std::memcpy((void *) tp_doc, rec.doc, size);
     }
 
     auto &internals = get_internals();
diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index af36340f3..9ab1ce9c0 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -110,13 +110,13 @@ inline wchar_t *widen_chars(const char *safe_arg) {
 #endif
 
 #    if defined(HAVE_BROKEN_MBSTOWCS) && HAVE_BROKEN_MBSTOWCS
-    size_t count = strlen(safe_arg);
+    size_t count = std::strlen(safe_arg);
 #    else
-    size_t count = mbstowcs(nullptr, safe_arg, 0);
+    size_t count = std::mbstowcs(nullptr, safe_arg, 0);
 #    endif
     if (count != static_cast<size_t>(-1)) {
         widened_arg = new wchar_t[count + 1];
-        mbstowcs(widened_arg, safe_arg, count + 1);
+        std::mbstowcs(widened_arg, safe_arg, count + 1);
     }
 
 #if defined(_MSC_VER)
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index ec60429b1..344a18c56 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -23,7 +23,7 @@
 #include <string>
 #include <utility>
 
-#include <string.h>
+#include <cstring>
 
 #if defined(__cpp_lib_launder) && !(defined(_MSC_VER) && (_MSC_VER < 1914))
 #  define PYBIND11_STD_LAUNDER std::launder
@@ -327,8 +327,8 @@ protected:
                 a.descr = guarded_strdup(repr(a.value).cast<std::string>().c_str());
         }
 
-        rec->is_constructor
-            = (strcmp(rec->name, "__init__") == 0) || (strcmp(rec->name, "__setstate__") == 0);
+        rec->is_constructor = (std::strcmp(rec->name, "__init__") == 0)
+                              || (std::strcmp(rec->name, "__setstate__") == 0);
 
 #if !defined(NDEBUG) && !defined(PYBIND11_DISABLE_NEW_STYLE_INIT_WARNING)
         if (rec->is_constructor && !rec->is_new_style_constructor) {
@@ -409,10 +409,10 @@ protected:
             pybind11_fail("Internal error while parsing type signature (2)");
 
 #if PY_MAJOR_VERSION < 3
-        if (strcmp(rec->name, "__next__") == 0) {
+        if (std::strcmp(rec->name, "__next__") == 0) {
             std::free(rec->name);
             rec->name = guarded_strdup("next");
-        } else if (strcmp(rec->name, "__bool__") == 0) {
+        } else if (std::strcmp(rec->name, "__bool__") == 0) {
             std::free(rec->name);
             rec->name = guarded_strdup("__nonzero__");
         }
@@ -1302,8 +1302,8 @@ inline void call_operator_delete(void *p, size_t s, size_t a) {
 
 inline void add_class_method(object& cls, const char *name_, const cpp_function &cf) {
     cls.attr(cf.name()) = cf;
-    if (strcmp(name_, "__eq__") == 0 && !cls.attr("__dict__").contains("__hash__")) {
-      cls.attr("__hash__") = none();
+    if (std::strcmp(name_, "__eq__") == 0 && !cls.attr("__dict__").contains("__hash__")) {
+        cls.attr("__hash__") = none();
     }
 }