diff --git a/packages/common/src/models/activities.ts b/packages/common/src/models/activities.ts
index 7235300..ce9d5e4 100644
--- a/packages/common/src/models/activities.ts
+++ b/packages/common/src/models/activities.ts
@@ -1,7 +1,16 @@
 import { z } from "zod";
 
-export const Activity = z.object({
+export const Time = z.object({ hour: z.number(), minute: z.number() })
 
+export const Activity = z.object({
+    type: z.number(),
+    title: z.string(),
+    subtitle: z.string().optional(),
+    time: z.object({ start: Time, end: Time }),
+    lessons: z.object({ count: z.number(), first: z.date(), last: z.date() }),
+    price: z.number(),
+    color: z.string()
 })
 
+export type Time = z.infer<typeof Time>
 export type Activity = z.infer<typeof Activity>
diff --git a/packages/web/src/components/Calendar.astro b/packages/web/src/components/Calendar.astro
index 859759c..b5c0b3a 100644
--- a/packages/web/src/components/Calendar.astro
+++ b/packages/web/src/components/Calendar.astro
@@ -1,5 +1,6 @@
 ---
 import type { Activity } from "common";
+import { gcd } from "../lib/maths";
 
 interface Props {
   activities: Activity[][];
@@ -9,7 +10,25 @@ const { activities } = Astro.props;
 
 const timeMin = 8;
 const timeMax = 22;
-const timeStep = 1;
+const cellSize = 4;
+const minutesPerTick = 30;
+
+// NOTE: CSS grid does not allow to have fractional spans.
+// Therefore, it is needed to scale it by the smallest time interval in every activity.
+const minutes = [
+  ...activities.flat(2).reduce(
+    (set, activity) => {
+      set.add(activity.time.start.minute);
+      set.add(activity.time.end.minute);
+      return set;
+    },
+    new Set<number>([minutesPerTick]),
+  ),
+].filter((min) => min !== 0);
+const minuteScale = gcd(minutes);
+const gridScale = minutesPerTick / minuteScale;
+const timeStep = minutesPerTick / 60;
+const cellScale = gridScale / timeStep;
 
 function formatTime(time: number): string {
   const hour = Math.floor(time);
@@ -22,7 +41,7 @@ function formatTime(time: number): string {
   <div
     class="grid grid-cols-[auto_repeat(7,1fr)]"
     style={{
-      "grid-template-rows": `auto repeat(${(timeMax - timeMin) / timeStep}, 4rem)`,
+      "grid-template-rows": `auto repeat(${(timeMax - timeMin) * cellScale}, ${cellSize / cellScale}rem)`,
     }}
   >
     {
@@ -51,7 +70,7 @@ function formatTime(time: number): string {
         (_, row) => (
           <div
             class="col-span-full gridline"
-            style={{ width: "100%", "grid-row": row + 2 }}
+            style={{ width: "100%", "grid-row": row * gridScale + 2 }}
           />
         ),
       )
@@ -61,7 +80,7 @@ function formatTime(time: number): string {
       Array.from({ length: (timeMax - timeMin) / timeStep + 1 }).map((_, i) => (
         <div
           class="flex items-center col-start-1 -translate-y-1/2 pr-2"
-          style={{ "grid-row": i + 2 }}
+          style={{ "grid-row": i * gridScale + 2 }}
         >
           <span class="text-sm bg-white pr-1">
             {formatTime(timeMin + i * timeStep)}
@@ -69,6 +88,23 @@ function formatTime(time: number): string {
         </div>
       ))
     }
+
+    {
+      // --- Activity squares ---
+      activities.map((list, weekday) =>
+        list.map((activity) => (
+          <div
+            style={{
+              background: activity.color,
+              "grid-row": `${(activity.time.start.hour - timeMin) * cellScale + activity.time.start.minute / minuteScale + 2} / span ${(activity.time.end.hour - activity.time.start.hour) * cellScale + (activity.time.end.minute - activity.time.start.minute) / minuteScale}`,
+              "grid-column": ((weekday + 6) % 7) + 2,
+            }}
+          >
+            {activity.title} - {activity.subtitle}
+          </div>
+        )),
+      )
+    }
   </div>
 </div>
 
diff --git a/packages/web/src/lib/maths.test.ts b/packages/web/src/lib/maths.test.ts
index 096f939..5b0aa05 100644
--- a/packages/web/src/lib/maths.test.ts
+++ b/packages/web/src/lib/maths.test.ts
@@ -1,22 +1,7 @@
 import { describe, expect, test, } from "vitest";
-import { gcd, lcm } from "./maths";
+import { gcd, } from "./maths";
 
 describe("maths", function() {
-    test("lcm", function() {
-        const tests = [
-            { inputs: [1], expected: 1 },
-            { inputs: [1, 2], expected: 2 },
-            { inputs: [2, 3], expected: 6 },
-            { inputs: [2, 4], expected: 4 },
-            { inputs: [2, 3, 4], expected: 12 },
-            { inputs: [1, 3, 5, 8], expected: 120 },
-        ]
-
-        tests.forEach((test, i) => {
-            expect(lcm(test.inputs)).to.equal(test.expected, `tests[${i}]: expected ${test.inputs} to have ${test.expected} as lcm`);
-        })
-    })
-
     test("gcd", function() {
         const tests = [
             { inputs: [1], expected: 1 },
diff --git a/packages/web/src/lib/maths.ts b/packages/web/src/lib/maths.ts
index b437380..6b81ce7 100644
--- a/packages/web/src/lib/maths.ts
+++ b/packages/web/src/lib/maths.ts
@@ -25,25 +25,3 @@ export function gcd(n: number[]): number {
     }
     return stack[0]
 }
-
-/**
-* Lowest Common Multiple
-*/
-export function lcm(n: number[]): number {
-    if (n.length === 0) {
-        return 0
-    }
-
-    if (n.length <= 2) {
-        const product = n.reduce((p, curr) => p * curr, 1)
-        return product / gcd(n)
-    }
-
-    const stack = [...n]
-    while (stack.length >= 2) {
-        let a = stack.pop()!
-        let b = stack.pop()!
-        stack.push(lcm([a, b]))
-    }
-    return stack[0]
-}
diff --git a/packages/web/src/pages/horaire.astro b/packages/web/src/pages/horaire.astro
index 9116847..7b08c2f 100644
--- a/packages/web/src/pages/horaire.astro
+++ b/packages/web/src/pages/horaire.astro
@@ -10,19 +10,34 @@ const activities: Activity[][] = [
       type: 0,
       title: "Récréatif",
       subtitle: "6 ans et plus",
-      time: { start: 9, end: 10.5 },
+      time: { start: { hour: 8, minute: 0 }, end: { hour: 10, minute: 45 } },
       lessons: {
         count: 8,
         first: new Date(2025, 1, 6),
         last: new Date(2025, 5, 5),
       },
       price: 120,
+      color: "#ff00ff",
     },
   ],
   [],
   [],
   [],
-  [],
+  [
+    {
+      type: 0,
+      title: "Récréatif",
+      subtitle: "12 ans et plus",
+      time: { start: { hour: 10, minute: 15 }, end: { hour: 12, minute: 45 } },
+      lessons: {
+        count: 8,
+        first: new Date(2025, 1, 6),
+        last: new Date(2025, 5, 5),
+      },
+      price: 120,
+      color: "#ff0000",
+    },
+  ],
   [],
 ];
 ---