diff --git a/meson.build b/meson.build
index 8b8b36a096671136c8dff0840a91fe9c49a5f9af..a1dc8186d8b0c82a42fe718639f35c971b5f5d1f 100644
--- a/meson.build
+++ b/meson.build
@@ -78,6 +78,30 @@ nl_time_first_weekday_src = '''
 config_h.set('HAVE__NL_TIME_FIRST_WEEKDAY', cc.compiles(nl_time_first_weekday_src),
          description: 'Define if _NL_TIME_FIRST_WEEKDAY is available')
 
+# Not all systems support nl_langinfo (ALTMON_*)
+altmon_src = '''
+  /* _GNU_SOURCE is required by glibc 2.27.  */
+  #define _GNU_SOURCE
+  #include <langinfo.h>
+  int main() {
+    nl_langinfo (ALTMON_1);
+    nl_langinfo (ALTMON_2);
+    nl_langinfo (ALTMON_3);
+    nl_langinfo (ALTMON_4);
+    nl_langinfo (ALTMON_5);
+    nl_langinfo (ALTMON_6);
+    nl_langinfo (ALTMON_7);
+    nl_langinfo (ALTMON_8);
+    nl_langinfo (ALTMON_9);
+    nl_langinfo (ALTMON_10);
+    nl_langinfo (ALTMON_11);
+    nl_langinfo (ALTMON_12);
+  };
+'''
+
+config_h.set('HAVE_ALTMON', cc.compiles(altmon_src),
+         description: 'Define if ALTMON_* constants are available')
+
 # Compiler flags
 common_flags = [
   '-DHAVE_CONFIG_H',
diff --git a/src/gcal-date-chooser.c b/src/gcal-date-chooser.c
index 44268b6049fb6dd2c3e47f1f6a03857b05605cd0..238e16331a7a24dad19e1fb5788fa29af837fd2d 100644
--- a/src/gcal-date-chooser.c
+++ b/src/gcal-date-chooser.c
@@ -224,20 +224,6 @@ calendar_get_weekday_name (gint i)
   return text;
 }
 
-/* 0 = january */
-static gchar *
-calendar_get_month_name (gint i)
-{
-  GDateTime *date;
-  gchar *text;
-
-  date = g_date_time_new_local (2015, i + 1, 1, 1, 1, 1);
-  text = g_date_time_format (date, "%B");
-  g_date_time_unref (date);
-
-  return text;
-}
-
 static void
 calendar_init_weekday_display (GcalDateChooser *self)
 {
@@ -257,7 +243,7 @@ format_month (GcalMultiChoice *choice,
               gint             value,
               gpointer         data)
 {
-  return calendar_get_month_name (value);
+  return g_strdup (gcal_get_month_name (value));
 }
 
 static void
@@ -269,9 +255,8 @@ calendar_init_month_display (GcalDateChooser *self)
 
   for (i = 0; i < 12; i++)
     {
-      month = calendar_get_month_name (i);
-      months[i] = g_strdup_printf ("%s", month);
-      g_free (month);
+      month = gcal_get_month_name (i);
+      months[i] = g_strdup (month);
     }
 
   months[12] = NULL;
diff --git a/src/gcal-utils.c b/src/gcal-utils.c
index 9846a59bf2d76b0a7946f3b3719dafcd58429849..c7646565387412ceaabc3b04132403c37e73396d 100644
--- a/src/gcal-utils.c
+++ b/src/gcal-utils.c
@@ -20,6 +20,9 @@
 
 #define G_LOG_DOMAIN "Utils"
 
+/* langinfo.h in glibc 2.27 defines ALTMON_* only if _GNU_SOURCE is defined.  */
+#define _GNU_SOURCE
+
 #include "gcal-enums.h"
 #include "gcal-utils.h"
 #include "gcal-event-widget.h"
@@ -57,6 +60,29 @@ ab_day[7] =
 static const gint
 month_item[12] =
 {
+  /* ALTMON_* constants have been introduced in glibc 2.27 (Feb 1, 2018), also
+   * have been supported in *BSD family (but not in OS X) since 1990s.
+   * If they exist they are the correct way to obtain the month names in
+   * nominative case, standalone, without the day number, as used in the
+   * calendar header.  This is obligatory in some languages (Slavic, Baltic,
+   * Greek, etc.) but also recommended to use in all languages because for
+   * other languages there is no difference between ALTMON_* and MON_*.
+   * If ALTMON_* is not supported then we must use MON_*.
+   */
+#ifdef HAVE_ALTMON
+  ALTMON_1,
+  ALTMON_2,
+  ALTMON_3,
+  ALTMON_4,
+  ALTMON_5,
+  ALTMON_6,
+  ALTMON_7,
+  ALTMON_8,
+  ALTMON_9,
+  ALTMON_10,
+  ALTMON_11,
+  ALTMON_12
+#else
   MON_1,
   MON_2,
   MON_3,
@@ -69,6 +95,7 @@ month_item[12] =
   MON_10,
   MON_11,
   MON_12
+#endif
 };
 
 #define SCROLL_HARDNESS 10.0