diff --git a/app/static/css/app.css b/app/static/css/app.css
index ff68946..db2139d 100644
--- a/app/static/css/app.css
+++ b/app/static/css/app.css
@@ -1004,3 +1004,15 @@ body {
 .hidden {
     display: none !important;
 }
+
+/* Time text inputs (replacing type=time to avoid AM/PM) */
+.time-input {
+    font-variant-numeric: tabular-nums;
+    letter-spacing: 0.5px;
+    text-align: center;
+}
+
+.time-input.input-error {
+    border-color: var(--danger) !important;
+    background: #fff5f5;
+}
diff --git a/app/static/index.html b/app/static/index.html
index c9ee739..8e633f6 100644
--- a/app/static/index.html
+++ b/app/static/index.html
@@ -191,11 +191,11 @@
                 <div class="form-row">
                     <div class="form-group">
                         <label>Začátek</label>
-                        <input type="time" id="modalBlockStart" step="900">
+                        <input type="text" id="modalBlockStart" placeholder="HH:MM" maxlength="5" class="time-input" autocomplete="off">
                     </div>
                     <div class="form-group">
                         <label>Konec</label>
-                        <input type="time" id="modalBlockEnd" step="900">
+                        <input type="text" id="modalBlockEnd" placeholder="HH:MM" maxlength="5" class="time-input" autocomplete="off">
                     </div>
                 </div>
                 <div class="form-group">
diff --git a/app/static/js/app.js b/app/static/js/app.js
index 1a7624e..e72c0ea 100644
--- a/app/static/js/app.js
+++ b/app/static/js/app.js
@@ -293,8 +293,10 @@ const App = {
         const responsible = document.getElementById('modalBlockResponsible').value.trim() || null;
         const notes = document.getElementById('modalBlockNotes').value.trim() || null;
 
+        const timeRe = /^\d{2}:\d{2}$/;
         if (!title) { this.toast('Zadejte název bloku', 'error'); return; }
         if (!start || !end) { this.toast('Zadejte čas začátku a konce', 'error'); return; }
+        if (!timeRe.test(start) || !timeRe.test(end)) { this.toast('Neplatný formát času (HH:MM)', 'error'); return; }
 
         if (blockId) {
             // Edit existing block (no series expansion on edit — user edits only this one)
@@ -370,7 +372,48 @@ const App = {
 
     // ─── Events ───────────────────────────────────────────────────────
 
+    // ─── Time input helpers ───────────────────────────────────────────
+
+    _initTimeInput(el) {
+        // Auto-format: allow only digits + colon, insert ':' after 2 digits
+        el.addEventListener('input', (e) => {
+            let v = e.target.value.replace(/[^0-9:]/g, '');
+            // Strip colons and rebuild
+            const digits = v.replace(/:/g, '');
+            if (digits.length >= 3) {
+                v = digits.slice(0, 2) + ':' + digits.slice(2, 4);
+            } else {
+                v = digits;
+            }
+            e.target.value = v;
+        });
+        el.addEventListener('blur', (e) => {
+            const v = e.target.value;
+            if (!v) return;
+            // Validate HH:MM format
+            if (!/^\d{2}:\d{2}$/.test(v)) {
+                e.target.classList.add('input-error');
+                this.toast('Neplatný čas (formát HH:MM)', 'error');
+            } else {
+                const [h, m] = v.split(':').map(Number);
+                if (h > 23 || m > 59) {
+                    e.target.classList.add('input-error');
+                    this.toast('Neplatný čas (00:00–23:59)', 'error');
+                } else {
+                    e.target.classList.remove('input-error');
+                }
+            }
+        });
+        el.addEventListener('focus', (e) => {
+            e.target.classList.remove('input-error');
+        });
+    },
+
     bindEvents() {
+        // Init time inputs
+        this._initTimeInput(document.getElementById('modalBlockStart'));
+        this._initTimeInput(document.getElementById('modalBlockEnd'));
+
         // Import JSON
         document.getElementById('importJsonInput').addEventListener('change', (e) => {
             if (e.target.files[0]) importJson(e.target.files[0]);