diff --git a/internal_filesystem/apps/cz.ucw.pavel.calendar/META-INF/MANIFEST.JSON b/internal_filesystem/apps/cz.ucw.pavel.calendar/META-INF/MANIFEST.JSON
new file mode 100644
index 00000000..b2f079cc
--- /dev/null
+++ b/internal_filesystem/apps/cz.ucw.pavel.calendar/META-INF/MANIFEST.JSON
@@ -0,0 +1,24 @@
+{
+"name": "Calendar",
+"publisher": "micropythonos",
+"short_description": "Calendar",
+"long_description": "Simple calendar app.",
+"icon_url": "https://apps.micropythonos.com/apps/cz.ucw.pavel.columns/icons/cz.ucw.pavel.columns_0.0.1_64x64.png",
+"download_url": "https://apps.micropythonos.com/apps/cz.ucw.pavel.columns/mpks/cz.ucw.pavel.columns_0.0.1.mpk",
+"fullname": "cz.ucw.pavel.columns",
+"version": "0.0.1",
+"category": "utilities",
+"activities": [
+    {
+      "entrypoint": "assets/main.py",
+      "classname": "Main",
+      "intent_filters": [
+        {
+          "action": "main",
+          "category": "utilities"
+        }
+      ]
+    }
+  ]
+}
+
diff --git a/internal_filesystem/apps/cz.ucw.pavel.calendar/assets/main.py b/internal_filesystem/apps/cz.ucw.pavel.calendar/assets/main.py
new file mode 100644
index 00000000..54708487
--- /dev/null
+++ b/internal_filesystem/apps/cz.ucw.pavel.calendar/assets/main.py
@@ -0,0 +1,560 @@
+from mpos import Activity
+
+"""
+
+Create simple calendar application. On main screen, it should have
+current time, date, and month overview. Current date and dates with
+events should be highlighted. There should be list of upcoming events.
+
+When date is clicked, dialog with adding event for that date should be
+displayed. Multi-day events should be supported.
+
+Data should be read/written to emacs org compatible text file.
+
+
+"""
+
+import time
+import os
+
+try:
+    import lvgl as lv
+except ImportError:
+    pass
+
+from mpos import Activity, MposKeyboard
+
+
+ORG_FILE = f"data/calendar.org"   # adjust for your device
+MAX_UPCOMING = 8
+
+
+# ------------------------------------------------------------
+# Small date helpers (no datetime module assumed)
+# ------------------------------------------------------------
+
+def is_leap_year(y):
+    return (y % 4 == 0 and y % 100 != 0) or (y % 400 == 0)
+
+
+def days_in_month(y, m):
+    if m == 2:
+        return 29 if is_leap_year(y) else 28
+    if m in (1, 3, 5, 7, 8, 10, 12):
+        return 31
+    return 30
+
+
+def ymd_to_int(y, m, d):
+    return y * 10000 + m * 100 + d
+
+
+def int_to_ymd(v):
+    y = v // 10000
+    m = (v // 100) % 100
+    d = v % 100
+    return y, m, d
+
+
+def weekday_name(idx):
+    # MicroPython localtime(): 0=Mon..6=Sun typically
+    names = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]
+    if 0 <= idx < 7:
+        return names[idx]
+    return "???"
+
+
+def first_weekday_of_month(y, m):
+    # brute-force using time.mktime if available
+    # Some ports support it, some don't.
+    # If it fails, we fallback to "Monday".
+    try:
+        # localtime tuple: (y,m,d,h,mi,s,wd,yd)
+        t = time.mktime((y, m, 1, 0, 0, 0, 0, 0))
+        wd = time.localtime(t)[6]
+        return wd
+    except Exception:
+        return 0
+
+
+# ------------------------------------------------------------
+# Org event model + parser/writer
+# ------------------------------------------------------------
+
+class Event:
+    def __init__(self, title, start_ymd, end_ymd, start_time=None, end_time=None):
+        self.title = title
+        self.start = start_ymd  # int yyyymmdd
+        self.end = end_ymd      # int yyyymmdd
+        self.start_time = start_time  # "HH:MM" or None
+        self.end_time = end_time      # "HH:MM" or None
+
+    def is_multi_day(self):
+        return self.end != self.start
+
+    def occurs_on(self, ymd):
+        return self.start <= ymd <= self.end
+
+    def start_key(self):
+        return self.start
+
+
+class OrgCalendarStore:
+    def __init__(self, path):
+        self.path = path
+
+    def load(self):
+        if not self._exists(self.path):
+            return []
+
+        try:
+            with open(self.path, "r", encoding="utf-8") as f:
+                lines = f.read().splitlines()
+        except Exception:
+            # fallback without encoding kw if unsupported
+            with open(self.path, "r") as f:
+                lines = f.read().splitlines()
+
+        events = []
+        current_title = None
+        # FIXME this likely does not work
+
+        for line in lines:
+            line = line.strip()
+
+            if line.startswith("** "):
+                current_title = line[3:].strip()
+                continue
+
+            if not line.startswith("<"):
+                continue
+
+            ev = self._parse_timestamp_line(current_title, line)
+            if ev:
+                events.append(ev)
+
+        events.sort(key=lambda e: e.start_key())
+        return events
+
+    def save_append(self, event):
+        # Create file if missing
+        if not self._exists(self.path):
+            self._write_text("* Events\n")
+
+        # Append event
+        out = []
+        out.append("** " + event.title)
+
+        if event.start == event.end:
+            y, m, d = int_to_ymd(event.start)
+            wd = weekday_name(self._weekday_for_ymd(y, m, d))
+            if event.start_time and event.end_time:
+                out.append("<%04d-%02d-%02d %s %s-%s>" % (
+                    y, m, d, wd, event.start_time, event.end_time
+                ))
+            else:
+                out.append("<%04d-%02d-%02d %s>" % (y, m, d, wd))
+        else:
+            y1, m1, d1 = int_to_ymd(event.start)
+            y2, m2, d2 = int_to_ymd(event.end)
+            wd1 = weekday_name(self._weekday_for_ymd(y1, m1, d1))
+            wd2 = weekday_name(self._weekday_for_ymd(y2, m2, d2))
+            out.append("<%04d-%02d-%02d %s>--<%04d-%02d-%02d %s>" % (
+                y1, m1, d1, wd1,
+                y2, m2, d2, wd2
+            ))
+
+        out.append("")  # blank line
+        self._append_text("\n".join(out) + "\n")
+
+    # --------------------
+
+    def _parse_timestamp_line(self, title, line):
+        if not title:
+            return None
+
+        # Single-day: <2026-02-05 Thu>
+        # With time:  <2026-02-05 Thu 10:00-11:00>
+        # Range:      <2026-02-10 Tue>--<2026-02-14 Sat>
+
+        if "--<" in line:
+            a, b = line.split("--", 1)
+            s = self._parse_one_timestamp(a)
+            e = self._parse_one_timestamp(b)
+            if not s or not e:
+                return None
+            return Event(title, s["ymd"], e["ymd"], None, None)
+
+        s = self._parse_one_timestamp(line)
+        if not s:
+            return None
+
+        return Event(title, s["ymd"], s["ymd"], s.get("start_time"), s.get("end_time"))
+
+    def _parse_one_timestamp(self, token):
+        token = token.strip()
+        if not (token.startswith("<") and token.endswith(">")):
+            return None
+
+        inner = token[1:-1].strip()
+        parts = inner.split()
+
+        # Expect YYYY-MM-DD ...
+        if len(parts) < 2:
+            return None
+
+        date_s = parts[0]
+        try:
+            y = int(date_s[0:4])
+            m = int(date_s[5:7])
+            d = int(date_s[8:10])
+        except Exception:
+            return None
+
+        ymd = ymd_to_int(y, m, d)
+
+        # Optional time part like 10:00-11:00
+        start_time = None
+        end_time = None
+        if len(parts) >= 3 and "-" in parts[2]:
+            t = parts[2]
+            if len(t) == 11 and t[2] == ":" and t[5] == "-" and t[8] == ":":
+                start_time = t[0:5]
+                end_time = t[6:11]
+
+        return {
+            "ymd": ymd,
+            "start_time": start_time,
+            "end_time": end_time
+        }
+
+    def _exists(self, path):
+        try:
+            os.stat(path)
+            return True
+        except Exception:
+            return False
+
+    def _append_text(self, s):
+        with open(self.path, "a") as f:
+            f.write(s)
+
+    def _write_text(self, s):
+        with open(self.path, "w") as f:
+            f.write(s)
+
+    def _weekday_for_ymd(self, y, m, d):
+        try:
+            t = time.mktime((y, m, d, 0, 0, 0, 0, 0))
+            return time.localtime(t)[6]
+        except Exception:
+            return 0
+
+
+# ------------------------------------------------------------
+# Calendar Activity
+# ------------------------------------------------------------
+
+class Main(Activity):
+
+    def __init__(self):
+        super().__init__()
+
+        self.store = OrgCalendarStore(ORG_FILE)
+        self.events = []
+
+        self.timer = None
+
+        # UI
+        self.screen = None
+        self.lbl_time = None
+        self.lbl_date = None
+        self.lbl_month = None
+
+        self.grid = None
+        self.day_buttons = []
+
+        self.upcoming_list = None
+
+        # Current month shown
+        self.cur_y = 0
+        self.cur_m = 0
+        self.today_ymd = 0
+
+    # --------------------
+
+    def onCreate(self):
+        self.screen = lv.obj()
+        #self.screen.remove_flag(lv.obj.FLAG.SCROLLABLE)
+
+        # Top labels
+        self.lbl_time = lv.label(self.screen)
+        self.lbl_time.set_style_text_font(lv.font_montserrat_20, 0)
+        self.lbl_time.align(lv.ALIGN.TOP_LEFT, 6, 4)
+
+        self.lbl_date = lv.label(self.screen)
+        self.lbl_date.align(lv.ALIGN.TOP_LEFT, 6, 40)
+
+        self.lbl_month = lv.label(self.screen)
+        self.lbl_month.align(lv.ALIGN.TOP_RIGHT, -6, 10)
+
+        # Upcoming events list
+        self.upcoming_list = lv.list(self.screen)
+        self.upcoming_list.set_size(lv.pct(90), 60)
+        self.upcoming_list.align_to(self.lbl_date, lv.ALIGN.OUT_BOTTOM_LEFT, 0, 10)
+
+        # Month grid container
+        self.grid = lv.obj(self.screen)
+        self.grid.set_size(lv.pct(90), 60)
+        self.grid.set_style_border_width(1, 0)
+        self.grid.set_style_pad_all(0, 0)
+        self.grid.set_style_radius(6, 0)
+        self.grid.align_to(self.upcoming_list, lv.ALIGN.OUT_BOTTOM_LEFT, 0, 10)
+
+        self.setContentView(self.screen)
+
+        self.reload_data()
+        print("My events == ", self.events)
+        self.build_month_view()
+        self.refresh_upcoming()
+
+    def onResume(self, screen):
+        self.timer = lv.timer_create(self.tick, 30000, None)
+        self.tick(0)
+
+    def onPause(self, screen):
+        if self.timer:
+            self.timer.delete()
+            self.timer = None
+
+    # --------------------
+
+    def reload_data(self):
+        print("Loading...")
+        self.events = self.store.load()
+        # FIXME
+        #self.events = [ Event("Test event", 20260207, 20260208) ]
+
+    def tick(self, t):
+        now = time.localtime()
+        y, m, d = now[0], now[1], now[2]
+        hh, mm, ss = now[3], now[4], now[5]
+        wd = weekday_name(now[6])
+
+        self.today_ymd = ymd_to_int(y, m, d)
+
+        self.lbl_time.set_text("%02d:%02d" % (hh, mm))
+        self.lbl_date.set_text("%04d-%02d-%02d %s" % (y, m, d, wd))
+
+        # Month label
+        self.lbl_month.set_text("%04d-%02d" % (self.cur_y, self.cur_m))
+
+        # Re-highlight today (cheap)
+        self.update_day_highlights()
+
+    # --------------------
+
+    def build_month_view(self):
+        now = time.localtime()
+        self.cur_y, self.cur_m = now[0], now[1]
+
+        # Determine size
+        d = lv.display_get_default()
+        w = d.get_horizontal_resolution()
+
+        cell = w // 8
+        grid_w = cell * 7 + 8
+        grid_h = cell * 6 + 8
+
+        self.grid.set_size(grid_w, grid_h)
+
+        # Clear old buttons
+        for b in self.day_buttons:
+            b.delete()
+        self.day_buttons = []
+        self.day_of_btn = {}
+
+        first_wd = first_weekday_of_month(self.cur_y, self.cur_m)  # 0=Mon
+        dim = days_in_month(self.cur_y, self.cur_m)
+
+        # LVGL grid is easiest as absolute positioning here
+        for day in range(1, dim + 1):
+            idx = (first_wd + (day - 1))
+            row = idx // 7
+            col = idx % 7
+
+            btn = lv.button(self.grid)
+            btn.set_size(cell - 2, cell - 2)
+            btn.set_pos(4 + col * cell, 4 + row * cell)
+            btn.add_event_cb(lambda e, dd=day: self.on_day_clicked(dd), lv.EVENT.CLICKED, None)
+
+            lbl = lv.label(btn)
+            lbl.set_text(str(day))
+            lbl.center()
+
+            self.day_buttons.append(btn)
+            self.day_of_btn[btn] = day
+
+        self.update_day_highlights()
+
+    def update_day_highlights(self):
+        for btn in self.day_buttons:
+            day = self.day_of_btn.get(btn, None)
+            if day is None:
+                continue
+
+            ymd = ymd_to_int(self.cur_y, self.cur_m, day)
+
+            has_event = self.day_has_event(ymd)
+            is_today = (ymd == self.today_ymd)
+            #print(ymd, has_event, is_today)
+
+            if is_today:
+                btn.set_style_bg_color(lv.palette_main(lv.PALETTE.BLUE), 0)
+            elif has_event:
+                btn.set_style_bg_color(lv.palette_main(lv.PALETTE.GREEN), 0)
+            else:
+                btn.set_style_bg_color(lv.palette_main(lv.PALETTE.GREY), 0)
+
+    def day_has_event(self, ymd):
+        for e in self.events:
+            if e.occurs_on(ymd):
+                return True
+        return False
+
+    # --------------------
+
+    def refresh_upcoming(self):
+        self.upcoming_list.clean()
+
+        now = time.localtime()
+        today = ymd_to_int(now[0], now[1], now[2])
+
+        upcoming = []
+        for e in self.events:
+            if e.end >= today:
+                upcoming.append(e)
+
+        upcoming.sort(key=lambda e: e.start)
+
+        for e in upcoming[:MAX_UPCOMING]:
+            y1, m1, d1 = int_to_ymd(e.start)
+            y2, m2, d2 = int_to_ymd(e.end)
+
+            if e.start == e.end:
+                date_s = "%04d-%02d-%02d" % (y1, m1, d1)
+            else:
+                date_s = "%04d-%02d-%02d..%04d-%02d-%02d" % (y1, m1, d1, y2, m2, d2)
+
+            txt = date_s + " " + e.title
+            self.upcoming_list.add_text(txt)
+
+        self.upcoming_list.add_text("that's all folks")
+
+    # --------------------
+
+    def on_day_clicked(self, day):
+        print("Day clicked")
+        ymd = ymd_to_int(self.cur_y, self.cur_m, day)
+        self.open_add_dialog(ymd)
+
+    def open_add_dialog(self, ymd):
+        y, m, d = int_to_ymd(ymd)
+
+        dlg = lv.obj(self.screen)
+        dlg.set_size(lv.pct(100), 480)
+        dlg.center()
+        dlg.set_style_bg_color(lv.color_hex(0x8f8f8f), 0)
+        dlg.set_style_border_width(2, 0)
+        dlg.set_style_radius(10, 0)
+
+        title = lv.label(dlg)
+        title.set_text("Add event")
+        title.align(lv.ALIGN.TOP_MID, 0, 8)
+
+        date_lbl = lv.label(dlg)
+        date_lbl.set_text("%04d-%02d-%02d" % (y, m, d))
+        date_lbl.align_to(title, lv.ALIGN.OUT_BOTTOM_MID, 0, 10)
+
+        # Title input
+        ti = lv.textarea(dlg)
+        ti.set_size(220, 32)
+        ti.align_to(date_lbl, lv.ALIGN.OUT_BOTTOM_MID, 0, 10)
+        ti.set_placeholder_text("Title")
+        keyboard = MposKeyboard(dlg)
+        keyboard.set_textarea(ti)
+        #keyboard.add_flag(lv.obj.FLAG.HIDDEN)
+
+        # End date offset (days)
+        end_lbl = lv.label(dlg)
+        end_lbl.set_text("Duration days:")
+        end_lbl.align_to(ti, lv.ALIGN.OUT_BOTTOM_MID, 0, 10)
+
+        dd = lv.dropdown(dlg)
+        dd.set_options("1\n2\n3\n4\n5\n6\n7\n10\n14\n21\n30")
+        dd.set_selected(0)
+        dd.set_size(70, 32)
+        dd.align_to(end_lbl, lv.ALIGN.OUT_BOTTOM_MID, 0, 10)
+
+        # Buttons
+        btn_cancel = lv.button(dlg)
+        btn_cancel.set_size(90, 30)
+        btn_cancel.align(lv.ALIGN.TOP_LEFT, 12, 10)
+        btn_cancel.add_event_cb(lambda e: dlg.delete(), lv.EVENT.CLICKED, None)
+        lc = lv.label(btn_cancel)
+        lc.set_text("Cancel")
+        lc.center()
+
+        btn_add = lv.button(dlg)
+        btn_add.set_size(90, 30)
+        btn_add.align(lv.ALIGN.TOP_RIGHT, -12, 10)
+
+        def do_add(e):
+            title_s = ti.get_text()
+            if not title_s or title_s.strip() == "":
+                return
+
+            dur_s = 1 # dd.get_selected_str() FIXME
+            try:
+                dur = int(dur_s)
+            except Exception:
+                dur = 1
+
+            end_ymd = self.add_days(ymd, dur - 1)
+
+            ev = Event(title_s.strip(), ymd, end_ymd, None, None)
+            self.events.append(ev)
+            self.store.save_append(ev) # FIXME
+
+            # Reload + refresh UI
+            # FIXME: common code?
+            #self.reload_data()
+            self.update_day_highlights()
+            self.refresh_upcoming()
+
+            dlg.delete()
+
+        btn_add.add_event_cb(do_add, lv.EVENT.CLICKED, None)
+        la = lv.label(btn_add)
+        la.set_text("Add")
+        la.center()
+
+    # --------------------
+
+    def add_days(self, ymd, days):
+        # simple date add (forward only), no datetime dependency
+        y, m, d = int_to_ymd(ymd)
+
+        while days > 0:
+            d += 1
+            dim = days_in_month(y, m)
+            if d > dim:
+                d = 1
+                m += 1
+                if m > 12:
+                    m = 1
+                    y += 1
+            days -= 1
+
+        return ymd_to_int(y, m, d)
+
diff --git a/internal_filesystem/apps/cz.ucw.pavel.calendar/res/mipmap-mdpi/icon_64x64.png b/internal_filesystem/apps/cz.ucw.pavel.calendar/res/mipmap-mdpi/icon_64x64.png
new file mode 100644
index 00000000..ee72f838
Binary files /dev/null and b/internal_filesystem/apps/cz.ucw.pavel.calendar/res/mipmap-mdpi/icon_64x64.png differ