diff --git a/backend/sql/version_1.sql b/backend/sql/version_1.sql
index 17c432e..61d72a5 100644
--- a/backend/sql/version_1.sql
+++ b/backend/sql/version_1.sql
@@ -17,6 +17,8 @@ CREATE TABLE [User] (
 
     [default_servings] INTEGER DEFAULT 4,
     [lang] TEXT NOT NULL DEFAULT 'en',
+    -- 0: Monday, 1: Tuesday, 2: Wednesday, 3: Thursday, 4: Friday, 5: Saturday, 6: Sunday.
+    [first_day_of_the_week] INTEGER DEFAULT 0,
 
     [password] TEXT NOT NULL, -- argon2(password_plain, salt).
 
@@ -34,6 +36,17 @@ CREATE TABLE [User] (
 CREATE INDEX [validation_token_index] ON [User]([validation_token]);
 CREATE UNIQUE INDEX [User_email_index] ON [User]([email]);
 
+CREATE TRIGGER [User_trigger_update_first_day_of_the_week]
+BEFORE UPDATE OF [first_day_of_the_week]
+ON [User]
+BEGIN
+    SELECT
+        CASE
+            WHEN NEW.[first_day_of_the_week] < 0 OR NEW.[first_day_of_the_week] > 6 THEN
+                RAISE (ABORT, 'Invalid [first_day_of_the_week] value')
+        END;
+END;
+
 CREATE TABLE [UserLoginToken] (
     [id] INTEGER PRIMARY KEY,
     [user_id] INTEGER NOT NULL,
diff --git a/backend/src/data/db/user.rs b/backend/src/data/db/user.rs
index 51c71f4..bde7fe8 100644
--- a/backend/src/data/db/user.rs
+++ b/backend/src/data/db/user.rs
@@ -77,7 +77,7 @@ FROM [UserLoginToken] WHERE [token] = $1
 
     pub async fn load_user(&self, user_id: i64) -> Result<Option<model::User>> {
         sqlx::query_as(
-            "SELECT [id], [email], [name], [default_servings], [lang], [is_admin] FROM [User] WHERE [id] = $1",
+            "SELECT [id], [email], [name], [default_servings], [first_day_of_the_week], [lang], [is_admin] FROM [User] WHERE [id] = $1",
         )
         .bind(user_id)
         .fetch_optional(&self.pool)
@@ -93,16 +93,17 @@ FROM [UserLoginToken] WHERE [token] = $1
         new_email: Option<&str>,
         new_name: Option<&str>,
         new_default_servings: Option<u32>,
+        new_first_day_of_the_week: Option<Weekday>,
         new_password: Option<&str>,
     ) -> Result<UpdateUserResult> {
         let mut tx = self.tx().await?;
         let hashed_new_password = new_password.map(|p| hash(p).unwrap());
 
-        let (email, name, default_servings, hashed_password) = sqlx::query_as::<
+        let (email, name, default_servings, first_day_of_the_week, hashed_password) = sqlx::query_as::<
             _,
-            (String, String, u32, String),
+            (String, String, u32, u8, String),
         >(
-            "SELECT [email], [name], [default_servings], [password] FROM [User] WHERE [id] = $1",
+            "SELECT [email], [name], [default_servings], [first_day_of_the_week], [password] FROM [User] WHERE [id] = $1",
         )
         .bind(user_id)
         .fetch_one(&mut *tx)
@@ -148,7 +149,7 @@ WHERE [id] = $1
         sqlx::query(
             r#"
 UPDATE [User]
-SET [email] = $2, [name] = $3, [default_servings] = $4, [password] = $5
+SET [email] = $2, [name] = $3, [default_servings] = $4, [first_day_of_the_week] = $5, [password] = $6
 WHERE [id] = $1
             "#,
         )
@@ -156,6 +157,7 @@ WHERE [id] = $1
         .bind(new_email.unwrap_or(&email))
         .bind(new_name.map(str::trim).unwrap_or(&name))
         .bind(new_default_servings.unwrap_or(default_servings))
+        .bind(new_first_day_of_the_week.map(|d| d as u8).unwrap_or(first_day_of_the_week))
         .bind(hashed_new_password.unwrap_or(hashed_password))
         .execute(&mut *tx)
         .await?;
@@ -179,8 +181,13 @@ WHERE [id] = $1
             .map_err(DBError::from)
     }
 
-    pub async fn sign_up(&self, email: &str, password: &str) -> Result<SignUpResult> {
-        self.sign_up_with_given_time(email, password, Utc::now())
+    pub async fn sign_up(
+        &self,
+        email: &str,
+        password: &str,
+        first_day_of_the_week: Weekday,
+    ) -> Result<SignUpResult> {
+        self.sign_up_with_given_time(email, password, first_day_of_the_week, Utc::now())
             .await
     }
 
@@ -188,6 +195,7 @@ WHERE [id] = $1
         &self,
         email: &str,
         password: &str,
+        first_day_of_the_week: Weekday,
         datetime: DateTime<Utc>,
     ) -> Result<SignUpResult> {
         let mut tx = self.tx().await?;
@@ -229,11 +237,12 @@ WHERE [id] = $1
                 sqlx::query(
                     r#"
 INSERT INTO [User]
-([email], [creation_datetime], [validation_token], [validation_token_datetime], [password])
-VALUES ($1, $2, $3, $4, $5)
+([email], [first_day_of_the_week], [creation_datetime], [validation_token], [validation_token_datetime], [password])
+VALUES ($1, $2, $3, $4, $5, $6)
                     "#,
                 )
                 .bind(email)
+                .bind(first_day_of_the_week as u8)
                 .bind(Utc::now())
                 .bind(&token)
                 .bind(datetime)
@@ -525,7 +534,10 @@ mod tests {
     #[tokio::test]
     async fn sign_up() -> Result<()> {
         let connection = Connection::new_in_memory().await?;
-        match connection.sign_up("paul@atreides.com", "12345").await? {
+        match connection
+            .sign_up("paul@atreides.com", "12345", Weekday::Mon)
+            .await?
+        {
             SignUpResult::UserCreatedWaitingForValidation(_) => (), // Nominal case.
             other => panic!("{:?}", other),
         }
@@ -550,7 +562,10 @@ INSERT INTO
         NULL
     );
             "#)).await?;
-        match connection.sign_up("paul@atreides.com", "12345").await? {
+        match connection
+            .sign_up("paul@atreides.com", "12345", Weekday::Mon)
+            .await?
+        {
             SignUpResult::UserAlreadyExists => (), // Nominal case.
             other => panic!("{:?}", other),
         }
@@ -564,7 +579,7 @@ INSERT INTO
         let email = "paul@atreides.com";
         let password = "12345";
 
-        match connection.sign_up(email, password).await? {
+        match connection.sign_up(email, password, Weekday::Mon).await? {
             SignUpResult::UserCreatedWaitingForValidation(_) => (), // Nominal case.
             other => panic!("{:?}", other),
         }
@@ -600,7 +615,10 @@ VALUES (
 )
             "#
         ).bind(token)).await?;
-        match connection.sign_up("paul@atreides.com", "12345").await? {
+        match connection
+            .sign_up("paul@atreides.com", "12345", Weekday::Mon)
+            .await?
+        {
             SignUpResult::UserCreatedWaitingForValidation(_) => (), // Nominal case.
             other => panic!("{:?}", other),
         }
@@ -610,7 +628,10 @@ VALUES (
     #[tokio::test]
     async fn sign_up_then_send_validation_at_time() -> Result<()> {
         let connection = Connection::new_in_memory().await?;
-        let validation_token = match connection.sign_up("paul@atreides.com", "12345").await? {
+        let validation_token = match connection
+            .sign_up("paul@atreides.com", "12345", Weekday::Mon)
+            .await?
+        {
             SignUpResult::UserCreatedWaitingForValidation(token) => token, // Nominal case.
             other => panic!("{:?}", other),
         };
@@ -633,7 +654,12 @@ VALUES (
     async fn sign_up_then_send_validation_too_late() -> Result<()> {
         let connection = Connection::new_in_memory().await?;
         let validation_token = match connection
-            .sign_up_with_given_time("paul@atreides.com", "12345", Utc::now() - Duration::days(1))
+            .sign_up_with_given_time(
+                "paul@atreides.com",
+                "12345",
+                Weekday::Mon,
+                Utc::now() - Duration::days(1),
+            )
             .await?
         {
             SignUpResult::UserCreatedWaitingForValidation(token) => token, // Nominal case.
@@ -657,7 +683,10 @@ VALUES (
     #[tokio::test]
     async fn sign_up_then_send_validation_with_bad_token() -> Result<()> {
         let connection = Connection::new_in_memory().await?;
-        let _validation_token = match connection.sign_up("paul@atreides.com", "12345").await? {
+        let _validation_token = match connection
+            .sign_up("paul@atreides.com", "12345", Weekday::Mon)
+            .await?
+        {
             SignUpResult::UserCreatedWaitingForValidation(token) => token, // Nominal case.
             other => panic!("{:?}", other),
         };
@@ -685,7 +714,7 @@ VALUES (
         let password = "12345";
 
         // Sign up.
-        let validation_token = match connection.sign_up(email, password).await? {
+        let validation_token = match connection.sign_up(email, password, Weekday::Mon).await? {
             SignUpResult::UserCreatedWaitingForValidation(token) => token, // Nominal case.
             other => panic!("{:?}", other),
         };
@@ -724,7 +753,7 @@ VALUES (
         let password = "12345";
 
         // Sign up.
-        let validation_token = match connection.sign_up(email, password).await? {
+        let validation_token = match connection.sign_up(email, password, Weekday::Mon).await? {
             SignUpResult::UserCreatedWaitingForValidation(token) => token, // Nominal case.
             other => panic!("{:?}", other),
         };
@@ -778,7 +807,7 @@ VALUES (
         let password = "12345";
 
         // Sign up.
-        let validation_token = match connection.sign_up(email, password).await? {
+        let validation_token = match connection.sign_up(email, password, Weekday::Mon).await? {
             SignUpResult::UserCreatedWaitingForValidation(token) => token, // Nominal case.
             other => panic!("{:?}", other),
         };
@@ -855,7 +884,7 @@ VALUES (
         let new_password = "54321";
 
         // Sign up.
-        let validation_token = match connection.sign_up(email, password).await? {
+        let validation_token = match connection.sign_up(email, password, Weekday::Mon).await? {
             SignUpResult::UserCreatedWaitingForValidation(token) => token, // Nominal case.
             other => panic!("{:?}", other),
         };
@@ -946,6 +975,7 @@ VALUES
                 Some("muaddib@fremen.com"),
                 Some("muaddib"),
                 None,
+                None,
                 Some("Chani"),
             )
             .await?
diff --git a/backend/src/data/model.rs b/backend/src/data/model.rs
index 4ba52f8..087bac0 100644
--- a/backend/src/data/model.rs
+++ b/backend/src/data/model.rs
@@ -8,6 +8,10 @@ pub struct User {
     pub name: String,
     pub email: String,
     pub default_servings: u32,
+
+    #[sqlx(try_from = "u8")]
+    pub first_day_of_the_week: Weekday,
+
     pub lang: String,
     pub is_admin: bool,
 }
diff --git a/backend/src/main.rs b/backend/src/main.rs
index 82496d9..d668b64 100644
--- a/backend/src/main.rs
+++ b/backend/src/main.rs
@@ -89,6 +89,16 @@ struct Context {
     dark_theme: bool,
 }
 
+impl Context {
+    pub fn first_day_of_the_week(&self) -> Weekday {
+        if let Some(user) = &self.user {
+            user.first_day_of_the_week
+        } else {
+            self.tr.first_day_of_week()
+        }
+    }
+}
+
 // TODO: Should main returns 'Result'?
 #[tokio::main]
 async fn main() {
diff --git a/backend/src/services/user.rs b/backend/src/services/user.rs
index 82a7192..815dc16 100644
--- a/backend/src/services/user.rs
+++ b/backend/src/services/user.rs
@@ -141,7 +141,11 @@ pub async fn sign_up_post(
     }
 
     match connection
-        .sign_up(&form_data.email, &form_data.password_1)
+        .sign_up(
+            &form_data.email,
+            &form_data.password_1,
+            context.tr.first_day_of_week(),
+        )
         .await
     {
         Ok(db::user::SignUpResult::UserAlreadyExists) => {
@@ -691,6 +695,7 @@ pub struct EditUserForm {
     name: String,
     email: String,
     default_servings: u32,
+    first_day_of_the_week: chrono::Weekday,
     password_1: String,
     password_2: String,
 }
@@ -713,6 +718,11 @@ pub async fn edit_user_post(
     Extension(context): Extension<Context>,
     Form(form_data): Form<EditUserForm>,
 ) -> Result<Response> {
+    event!(
+        Level::DEBUG,
+        "First day of the week: {:?}",
+        form_data.first_day_of_the_week
+    );
     if let Some(ref user) = context.user {
         fn error_response(
             error: ProfileUpdateError,
@@ -783,6 +793,7 @@ pub async fn edit_user_post(
                 Some(email_trimmed),
                 Some(&form_data.name),
                 Some(form_data.default_servings),
+                Some(form_data.first_day_of_the_week),
                 new_password,
             )
             .await
diff --git a/backend/src/translation.rs b/backend/src/translation.rs
index 2ffac8d..7d330e3 100644
--- a/backend/src/translation.rs
+++ b/backend/src/translation.rs
@@ -1,5 +1,6 @@
 use std::{borrow::Borrow, fs::File, sync::LazyLock};
 
+use chrono::Weekday;
 use common::utils;
 use ron::de::from_reader;
 use serde::Deserialize;
@@ -80,6 +81,7 @@ pub enum Sentence {
     ProfileTitle,
     ProfileEmail,
     ProfileDefaultServings,
+    ProfileFirstDayOfWeek,
     ProfileNewPassword,
     ProfileFollowEmailTitle,
     ProfileFollowEmailLink,
@@ -126,6 +128,13 @@ pub enum Sentence {
     RecipeEstimatedTimeMinAbbreviation,
 
     // Calendar.
+    CalendarMonday,
+    CalendarTuesday,
+    CalendarWednesday,
+    CalendarThursday,
+    CalendarFriday,
+    CalendarSaturday,
+    CalendarSunday,
     CalendarMondayAbbreviation,
     CalendarTuesdayAbbreviation,
     CalendarWednesdayAbbreviation,
@@ -197,6 +206,13 @@ impl Tr {
     pub fn current_lang_and_territory_code(&self) -> String {
         format!("{}-{}", self.lang.code, self.lang.territory)
     }
+
+    pub fn first_day_of_week(&self) -> Weekday {
+        match (self.lang.code.as_ref(), self.lang.territory.as_ref()) {
+            ("en", "US") => Weekday::Sun,
+            _ => Weekday::Mon,
+        }
+    }
 }
 
 // #[macro_export]
diff --git a/backend/templates/base.html b/backend/templates/base.html
index dd78f02..1552082 100644
--- a/backend/templates/base.html
+++ b/backend/templates/base.html
@@ -1,5 +1,7 @@
 <!DOCTYPE html>
-<html lang="{{ context.tr.current_lang_and_territory_code() }}" data-user-logged="{{ context.user.is_some() }}" >
+<html lang="{{ context.tr.current_lang_and_territory_code() }}"
+    data-user-logged="{{ context.user.is_some() }}"
+    data-user-first-day-of-the-week="{{ context.first_day_of_the_week().to_string() }}">
     <head>
         <meta charset="utf-8">
         <meta name="viewport" content="width=device-width, initial-scale=1.0">
diff --git a/backend/templates/calendar.html b/backend/templates/calendar.html
index e5e079e..1112ae5 100644
--- a/backend/templates/calendar.html
+++ b/backend/templates/calendar.html
@@ -26,7 +26,7 @@
     </div>
 
     <ul class="weekdays">
-        {% for day in [
+        {% let day_names = [
             Sentence::CalendarMondayAbbreviation,
             Sentence::CalendarTuesdayAbbreviation,
             Sentence::CalendarWednesdayAbbreviation,
@@ -34,9 +34,16 @@
             Sentence::CalendarFridayAbbreviation,
             Sentence::CalendarSaturdayAbbreviation,
             Sentence::CalendarSundayAbbreviation,
-        ] %}
-            <li class="weekday">{{ context.tr.t(*day) }}</li>
+        ]  %}
+
+        {% for i in 0..7 %}
+            <li class="weekday">
+                {{ context.tr.t(*day_names[
+                        (i + context.first_day_of_the_week().num_days_from_monday() as usize) % 7
+                    ]) }}
+            </li>
         {% endfor %}
+
     </ul>
 
     <ul class="days">
diff --git a/backend/templates/profile.html b/backend/templates/profile.html
index dad1d96..46011c0 100644
--- a/backend/templates/profile.html
+++ b/backend/templates/profile.html
@@ -26,6 +26,14 @@
             autocapitalize="none" autocomplete="email" autofocus="autofocus">
         <span class="user-message">{{ message_email }}</span>
 
+        <label for="input-password-1">{{ context.tr.tp(Sentence::ProfileNewPassword, [Box::new(common::consts::MIN_PASSWORD_SIZE)]) }}</label>
+        <input id="input-password-1" type="password" name="password_1" autocomplete="new-password">
+        <span></span>
+
+        <label for="input-password-2">{{ context.tr.t(Sentence::ReEnterPassword) }}</label>
+        <input id="input-password-2" type="password" name="password_2" autocomplete="new-password">
+        <span class="user-message">{{ message_password }}</span>
+
         <label for="input-servings">{{ context.tr.t(Sentence::ProfileDefaultServings) }}</label>
         <input
             id="input-servings"
@@ -35,13 +43,30 @@
             value="{{ default_servings }}">
         <span></span>
 
-        <label for="input-password-1">{{ context.tr.tp(Sentence::ProfileNewPassword, [Box::new(common::consts::MIN_PASSWORD_SIZE)]) }}</label>
-        <input id="input-password-1" type="password" name="password_1" autocomplete="new-password">
-        <span></span>
-
-        <label for="input-password-2">{{ context.tr.t(Sentence::ReEnterPassword) }}</label>
-        <input id="input-password-2" type="password" name="password_2" autocomplete="new-password">
-        <span class="user-message">{{ message_password }}</span>
+        <label for="input-first-day-of-week">{{ context.tr.t(Sentence::ProfileFirstDayOfWeek) }}</label>
+        <select id="input-first-day-of-week" name="first_day_of_the_week">
+            <option value="Mon"
+                {%~ if user.first_day_of_the_week == chrono::Weekday::Mon %}
+                    selected
+                {% endif %}
+            >
+                {{ context.tr.t(Sentence::CalendarMonday) }}
+            </option>
+            <option value="Sat"
+                {%~ if user.first_day_of_the_week == chrono::Weekday::Sat %}
+                    selected
+                {% endif %}
+            >
+                {{ context.tr.t(Sentence::CalendarSaturday) }}
+            </option>
+            <option value="Sun"
+                {%~ if user.first_day_of_the_week == chrono::Weekday::Sun %}
+                    selected
+                {% endif %}
+            >
+                {{ context.tr.t(Sentence::CalendarSunday) }}
+            </option>
+        </select>
 
         <input type="submit" name="commit" value="{{ context.tr.t(Sentence::Save) }}">
     </form>
diff --git a/backend/translation.ron b/backend/translation.ron
index 39d1466..0745507 100644
--- a/backend/translation.ron
+++ b/backend/translation.ron
@@ -67,6 +67,7 @@
             (ProfileTitle, "Profile"),
             (ProfileEmail, "Email (need to be revalidated if changed)"),
             (ProfileDefaultServings, "Default servings"),
+            (ProfileFirstDayOfWeek, "First day of the week"),
             (ProfileNewPassword, "New password (minimum {} characters)"),
             (ProfileFollowEmailTitle, "Cooking Recipes: Email validation"),
             (ProfileFollowEmailLink, "Follow this link to validate this email address, {}"),
@@ -110,6 +111,13 @@
             (RecipeSomeServings, "{} servings"),
             (RecipeEstimatedTimeMinAbbreviation, "min"),
 
+            (CalendarMonday, "Monday"),
+            (CalendarTuesday, "Tuesday"),
+            (CalendarWednesday, "Wednesday"),
+            (CalendarThursday, "Thursday"),
+            (CalendarFriday, "Friday"),
+            (CalendarSaturday, "Saturday"),
+            (CalendarSunday, "Sunday"),
             (CalendarMondayAbbreviation, "Mon"),
             (CalendarTuesdayAbbreviation, "Tue"),
             (CalendarWednesdayAbbreviation, "Wed"),
@@ -207,6 +215,7 @@
             (ProfileTitle, "Profile"),
             (ProfileEmail, "Email (doit être revalidé si changé)"),
             (ProfileDefaultServings, "Nombre de portions par défaut"),
+            (ProfileFirstDayOfWeek, "Premier jour de la semaine"),
             (ProfileNewPassword, "Nouveau mot de passe (minimum {} caractères)"),
             (ProfileFollowEmailTitle, "Recettes de Cuisine: Validation de l'adresse email"),
             (ProfileFollowEmailLink, "Suivez ce lien pour valider l'adresse email, {}"),
@@ -250,6 +259,13 @@
             (RecipeSomeServings, "pour {} personnes"),
             (RecipeEstimatedTimeMinAbbreviation, "min"),
 
+            (CalendarMonday, "lundi"),
+            (CalendarTuesday, "mardi"),
+            (CalendarWednesday, "mercredi"),
+            (CalendarThursday, "jeudi"),
+            (CalendarFriday, "vendredi"),
+            (CalendarSaturday, "samedi"),
+            (CalendarSunday, "dimanche"),
             (CalendarMondayAbbreviation, "Lun"),
             (CalendarTuesdayAbbreviation, "Mar"),
             (CalendarWednesdayAbbreviation, "Mer"),
diff --git a/common/src/ron_api.rs b/common/src/ron_api.rs
index 62a25a9..87ca32c 100644
--- a/common/src/ron_api.rs
+++ b/common/src/ron_api.rs
@@ -63,7 +63,8 @@ pub struct SetRecipeEstimatedTime {
     pub estimated_time: Option<u32>,
 }
 
-#[derive(Serialize, Deserialize, Clone, PartialEq, Debug)]
+#[repr(u32)]
+#[derive(Serialize, Deserialize, Clone, Copy, PartialEq, Debug)]
 pub enum Difficulty {
     Unknown = 0,
     Easy = 1,
diff --git a/frontend/src/calendar.rs b/frontend/src/calendar.rs
index 4b5a1ef..aa18e4e 100644
--- a/frontend/src/calendar.rs
+++ b/frontend/src/calendar.rs
@@ -66,6 +66,7 @@ impl CalendarState {
 pub struct CalendarOptions {
     pub can_select_date: bool,
     pub with_link_and_remove: bool,
+    pub first_day_of_the_week: Weekday,
 }
 
 pub fn setup(
@@ -118,7 +119,10 @@ pub fn setup(
         // gloo::console::log!(event); // TODO: Remove.
 
         if target.class_name() == "number" && options.can_select_date {
-            let first_day = first_grid_day(state_clone.get_displayed_date());
+            let first_day = first_grid_day(
+                state_clone.get_displayed_date(),
+                options.first_day_of_the_week,
+            );
             let day_grid_id = target.parent_element().unwrap().id();
             let day_offset = day_grid_id[9..10].parse::<u64>().unwrap() * 7
                 + day_grid_id[10..11].parse::<u64>().unwrap();
@@ -212,7 +216,7 @@ fn display_month(
         }
     }
 
-    let first_day = first_grid_day(date);
+    let first_day = first_grid_day(date, options.first_day_of_the_week);
     let mut current = first_day;
 
     for i in 0..NB_CALENDAR_ROW {
@@ -302,11 +306,11 @@ fn display_month(
     });
 }
 
-fn first_grid_day(mut date: NaiveDate) -> NaiveDate {
+fn first_grid_day(mut date: NaiveDate, first_day_of_the_week: Weekday) -> NaiveDate {
     while (date - Days::new(1)).month() == date.month() {
         date = date - Days::new(1);
     }
-    while date.weekday() != Weekday::Mon {
+    while date.weekday() != first_day_of_the_week {
         date = date - Days::new(1);
     }
     date
diff --git a/frontend/src/lib.rs b/frontend/src/lib.rs
index b67f618..230b40a 100644
--- a/frontend/src/lib.rs
+++ b/frontend/src/lib.rs
@@ -44,6 +44,12 @@ pub fn main() -> Result<(), JsValue> {
         .map(|v| v == "true")
         .unwrap_or_default();
 
+    let first_day_of_the_week = selector::<HtmlElement>("html")
+        .dataset()
+        .get("userFirstDayOfTheWeek")
+        .map(|v| v.parse().unwrap_or(chrono::Weekday::Mon))
+        .unwrap_or(chrono::Weekday::Mon);
+
     match path[..] {
         ["recipe", "edit", id] => {
             let id = id.parse::<i64>().unwrap(); // TODO: remove unwrap.
@@ -51,11 +57,11 @@ pub fn main() -> Result<(), JsValue> {
         }
         ["recipe", "view", id] => {
             let id = id.parse::<i64>().unwrap(); // TODO: remove unwrap.
-            pages::recipe_view::setup_page(id, is_user_logged)
+            pages::recipe_view::setup_page(id, is_user_logged, first_day_of_the_week)
         }
         ["dev_panel"] => pages::dev_panel::setup_page(),
         // Home.
-        [""] => pages::home::setup_page(is_user_logged),
+        [""] => pages::home::setup_page(is_user_logged, first_day_of_the_week),
         _ => log!("Path unknown: ", location),
     }
 
diff --git a/frontend/src/pages/home.rs b/frontend/src/pages/home.rs
index 4dabbd2..a4db1ca 100644
--- a/frontend/src/pages/home.rs
+++ b/frontend/src/pages/home.rs
@@ -1,3 +1,4 @@
+use chrono::Weekday;
 use gloo::events::EventListener;
 use wasm_bindgen::prelude::*;
 use wasm_bindgen_futures::spawn_local;
@@ -10,7 +11,7 @@ use crate::{
     utils::{SelectorExt, by_id, get_current_lang, get_locale, selector},
 };
 
-pub fn setup_page(is_user_logged: bool) {
+pub fn setup_page(is_user_logged: bool, first_day_of_the_week: Weekday) {
     let recipe_scheduler = RecipeScheduler::new(!is_user_logged);
 
     calendar::setup(
@@ -18,6 +19,7 @@ pub fn setup_page(is_user_logged: bool) {
         calendar::CalendarOptions {
             can_select_date: false,
             with_link_and_remove: true,
+            first_day_of_the_week,
         },
         recipe_scheduler,
     );
diff --git a/frontend/src/pages/recipe_view.rs b/frontend/src/pages/recipe_view.rs
index 899f924..6158c64 100644
--- a/frontend/src/pages/recipe_view.rs
+++ b/frontend/src/pages/recipe_view.rs
@@ -1,7 +1,8 @@
+use chrono::Weekday;
 use common::utils::substitute_with_names;
 use gloo::events::EventListener;
 use wasm_bindgen_futures::spawn_local;
-use web_sys::{Element, HtmlInputElement};
+use web_sys::{Element, HtmlElement, HtmlInputElement};
 
 use crate::{
     calendar, modal_dialog,
@@ -10,7 +11,7 @@ use crate::{
     utils::{SelectorExt, get_locale, selector},
 };
 
-pub fn setup_page(recipe_id: i64, is_user_logged: bool) {
+pub fn setup_page(recipe_id: i64, is_user_logged: bool, first_day_of_the_week: Weekday) {
     let recipe_scheduler = RecipeScheduler::new(!is_user_logged);
 
     let add_to_planner: Element = selector("#recipe-view .add-to-planner");
@@ -26,6 +27,7 @@ pub fn setup_page(recipe_id: i64, is_user_logged: bool) {
                             calendar::CalendarOptions {
                                 can_select_date: true,
                                 with_link_and_remove: false,
+                                first_day_of_the_week,
                             },
                             recipe_scheduler,
                         )