diff --git a/DOCUMENTATION/content/documentation/index.md b/DOCUMENTATION/content/documentation/index.md
index 9c74ac31..10ffefbd 100644
--- a/DOCUMENTATION/content/documentation/index.md
+++ b/DOCUMENTATION/content/documentation/index.md
@@ -1456,6 +1456,19 @@ e) set it to `true`
 
 
 
+<a name="Install php calendar extension"></a>
+## Install php calendar extension
+
+1 - Open the `.env` file
+<br>
+2 - Search for the `PHP_FPM_INSTALL_CALENDAR` argument under the PHP-FPM container
+<br>
+3 - Set it to `true`
+<br>
+4 - Re-build the containers `docker-compose build php-fpm`
+
+
+
 
 
 <br>
diff --git a/docker-compose.yml b/docker-compose.yml
index 2474f999..e717a44a 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -143,6 +143,7 @@ services:
           - INSTALL_SWOOLE=${PHP_FPM_INSTALL_SWOOLE}
           - INSTALL_IMAGE_OPTIMIZERS=${PHP_FPM_INSTALL_IMAGE_OPTIMIZERS}
           - INSTALL_IMAGEMAGICK=${PHP_FPM_INSTALL_IMAGEMAGICK}
+          - INSTALL_CALENDAR=${PHP_FPM_INSTALL_CALENDAR}
       volumes:
         - ./php-fpm/php${PHP_VERSION}.ini:/usr/local/etc/php/php.ini
         - ${APP_CODE_PATH_HOST}:${APP_CODE_PATH_CONTAINER}
diff --git a/env-example b/env-example
index 0f524098..ecd4c2ee 100644
--- a/env-example
+++ b/env-example
@@ -148,6 +148,7 @@ PHP_FPM_INSTALL_LDAP=false
 PHP_FPM_INSTALL_SWOOLE=false
 PHP_FPM_INSTALL_PG_CLIENT=false
 PHP_FPM_INSTALL_PCNTL=false
+PHP_FPM_INSTALL_CALENDAR=false
 
 ### PHP_WORKER ############################################
 
diff --git a/php-fpm/Dockerfile b/php-fpm/Dockerfile
index 92f81c18..8a76ab75 100644
--- a/php-fpm/Dockerfile
+++ b/php-fpm/Dockerfile
@@ -469,6 +469,19 @@ RUN if [ ${INSTALL_IMAP} = true ]; then \
     docker-php-ext-install imap \
 ;fi
 
+###########################################################################
+# Calendar:
+###########################################################################
+
+USER root
+
+ARG INSTALL_CALENDAR=false
+
+RUN if [ ${INSTALL_CALENDAR} = true ]; then \
+    docker-php-ext-configure calendar && \
+    docker-php-ext-install calendar \
+;fi
+
 ###########################################################################
 # Check PHP version:
 ###########################################################################