diff --git a/include/modules/clock.hpp b/include/modules/clock.hpp
index e54f4d2..bb63241 100644
--- a/include/modules/clock.hpp
+++ b/include/modules/clock.hpp
@@ -12,6 +12,11 @@
 
 namespace waybar::modules {
 
+struct waybar_time {
+  std::locale locale;
+  date::zoned_time<std::chrono::system_clock::duration> ztime;
+};
+
 class Clock : public ALabel {
  public:
   Clock(const std::string&, const Json::Value&);
@@ -23,6 +28,12 @@ class Clock : public ALabel {
   std::locale locale_;
   const date::time_zone* time_zone_;
   bool fixed_time_zone_;
+  date::year_month_day cached_calendar_ymd_;
+  std::string cached_calendar_text_;
+
+  auto calendar_text(const waybar_time& wtime) -> std::string;
+  auto weekdays_header(const date::weekday& first_dow, std::ostream& os) -> void;
+  auto first_day_of_week() -> date::weekday;
 };
 
 }  // namespace waybar::modules
diff --git a/man/waybar-clock.5.scd b/man/waybar-clock.5.scd
index e3213f3..6684d89 100644
--- a/man/waybar-clock.5.scd
+++ b/man/waybar-clock.5.scd
@@ -65,6 +65,10 @@ The *clock* module displays the current date and time.
 
 View all valid format options in *strftime(3)*.
 
+# FORMAT REPLACEMENTS
+
+*{calendar}*: Current month calendar
+
 # EXAMPLES
 
 ```
diff --git a/meson.build b/meson.build
index 69439ac..8cfe5d8 100644
--- a/meson.build
+++ b/meson.build
@@ -42,6 +42,22 @@ if not compiler.has_header('filesystem')
     endif
 endif
 
+code = '''
+#include <langinfo.h>
+#include <locale.h>
+int main(int argc, char** argv) {
+    locale_t locale = newlocale(LC_ALL, "en_US.UTF-8", nullptr);
+    char* str;
+    str = nl_langinfo_l(_NL_TIME_WEEK_1STDAY, locale);
+    str = nl_langinfo_l(_NL_TIME_FIRST_WEEKDAY, locale);
+    freelocale(locale);
+    return 0;
+}
+'''
+if compiler.links(code, name : 'nl_langinfo with _NL_TIME_WEEK_1STDAY, _NL_TIME_FIRST_WEEKDAY')
+    add_project_arguments('-DHAVE_LANGINFO_1STDAY', language: 'cpp')
+endif
+
 add_global_arguments(cpp_args, language : 'cpp')
 add_global_link_arguments(cpp_link_args, language : 'cpp')
 
diff --git a/resources/config b/resources/config
index fcc365e..237c787 100644
--- a/resources/config
+++ b/resources/config
@@ -65,7 +65,7 @@
     },
     "clock": {
         // "timezone": "America/New_York",
-        "tooltip-format": "{:%Y-%m-%d | %H:%M}",
+        "tooltip-format": "<big>{:%Y %B}</big>\n<tt><small>{calendar}</small></tt>",
         "format-alt": "{:%Y-%m-%d}"
     },
     "cpu": {
diff --git a/src/modules/clock.cpp b/src/modules/clock.cpp
index 38af115..5655168 100644
--- a/src/modules/clock.cpp
+++ b/src/modules/clock.cpp
@@ -1,4 +1,12 @@
 #include "modules/clock.hpp"
+#include <sstream>
+#include <type_traits>
+#ifdef HAVE_LANGINFO_1STDAY
+#include <langinfo.h>
+#include <locale.h>
+#endif
+
+using waybar::modules::waybar_time;
 
 waybar::modules::Clock::Clock(const std::string& id, const Json::Value& config)
     : ALabel(config, "clock", id, "{:%H:%M}", 60)
@@ -24,13 +32,6 @@ waybar::modules::Clock::Clock(const std::string& id, const Json::Value& config)
   };
 }
 
-using zoned_time = date::zoned_time<std::chrono::system_clock::duration>;
-
-struct waybar_time {
-  std::locale locale;
-  zoned_time ztime;
-};
-
 auto waybar::modules::Clock::update() -> void {
   if (!fixed_time_zone_) {
     // Time zone can change. Be sure to pick that.
@@ -44,15 +45,96 @@ auto waybar::modules::Clock::update() -> void {
 
   if (tooltipEnabled()) {
     if (config_["tooltip-format"].isString()) {
+      const auto calendar = calendar_text(wtime);
       auto tooltip_format = config_["tooltip-format"].asString();
-      auto tooltip_text = fmt::format(tooltip_format, wtime);
-      label_.set_tooltip_text(tooltip_text);
+      auto tooltip_text = fmt::format(tooltip_format, wtime, fmt::arg("calendar", calendar));
+      label_.set_tooltip_markup(tooltip_text);
     } else {
-      label_.set_tooltip_text(text);
+      label_.set_tooltip_markup(text);
     }
   }
 }
 
+auto waybar::modules::Clock::calendar_text(const waybar_time& wtime) -> std::string {
+  const auto daypoint = date::floor<date::days>(wtime.ztime.get_local_time());
+  const auto ymd = date::year_month_day(daypoint);
+  if (cached_calendar_ymd_ == ymd) {
+    return cached_calendar_text_;
+  }
+
+  const date::year_month ym(ymd.year(), ymd.month());
+  const auto curr_day = ymd.day();
+
+  std::stringstream os;
+  const auto first_dow = first_day_of_week();
+  weekdays_header(first_dow, os);
+
+  // First week prefixed with spaces if needed.
+  auto wd = date::weekday(ym/1);
+  auto empty_days = (wd - first_dow).count();
+  if (empty_days > 0) {
+    os << std::string(empty_days * 3 - 1, ' ');
+  }
+  auto last_day = (ym/date::literals::last).day();
+  for (auto d = date::day(1); d <= last_day; ++d, ++wd) {
+    if (wd != first_dow) {
+      os << ' ';
+    } else if (unsigned(d) != 1) {
+      os << '\n';
+    }
+    if (d == curr_day) {
+      os << "<b><u>" << date::format("%e", d) << "</u></b>";
+    } else {
+      os << date::format("%e", d);
+    }
+  }
+
+  auto result = os.str();
+  cached_calendar_ymd_ = ymd;
+  cached_calendar_text_ = result;
+  return result;
+}
+
+auto waybar::modules::Clock::weekdays_header(const date::weekday& first_dow, std::ostream& os) -> void {
+  auto wd = first_dow;
+  do {
+    if (wd != first_dow) os << ' ';
+    Glib::ustring wd_ustring(date::format(locale_, "%a", wd));
+    auto wd_len = wd_ustring.length();
+    if (wd_len > 2) {
+      wd_ustring = wd_ustring.substr(0, 2);
+      wd_len = 2;
+    }
+    const std::string pad(2 - wd_len, ' ');
+    os << pad << wd_ustring;
+  } while (++wd != first_dow);
+  os << "\n";
+}
+
+#ifdef HAVE_LANGINFO_1STDAY
+template <auto fn>
+using deleter_from_fn = std::integral_constant<decltype(fn), fn>;
+
+template <typename T, auto fn>
+using deleting_unique_ptr = std::unique_ptr<T, deleter_from_fn<fn>>;
+#endif
+
+// Computations done similarly to Linux cal utility.
+auto waybar::modules::Clock::first_day_of_week() -> date::weekday {
+#ifdef HAVE_LANGINFO_1STDAY
+  deleting_unique_ptr<std::remove_pointer<locale_t>::type, freelocale>
+    posix_locale{newlocale(LC_ALL, locale_.name().c_str(), nullptr)};
+  if (posix_locale) {
+    const int i = (std::intptr_t) nl_langinfo_l(_NL_TIME_WEEK_1STDAY, posix_locale.get());
+    auto ymd = date::year(i / 10000)/(i / 100 % 100)/(i % 100);
+    auto wd = date::weekday(ymd);
+    uint8_t j = *nl_langinfo_l(_NL_TIME_FIRST_WEEKDAY, posix_locale.get());
+    return wd + date::days(j - 1);
+  }
+#endif
+  return date::Sunday;
+}
+
 template <>
 struct fmt::formatter<waybar_time> : fmt::formatter<std::tm> {
   template <typename FormatContext>