diff --git a/api/js/jsapi/egw_timer.js b/api/js/jsapi/egw_timer.js
index 5bacad9c98..c8170555c7 100644
--- a/api/js/jsapi/egw_timer.js
+++ b/api/js/jsapi/egw_timer.js
@@ -518,13 +518,17 @@ egw.extend('timer', egw.MODULE_GLOBAL, function()
 						if (pref === 'no') return;
 
 						// overall timer not running, ask to start
-						if (overall && !overall.start)
+						if (overall && !overall.start && !state.overall.dont_ask)
 						{
 							Et2Dialog.show_dialog((button) => {
 								if (button === Et2Dialog.YES_BUTTON)
 								{
 									timerAction('overall-start');
 								}
+								else
+								{
+									egw.request('EGroupware\\Timesheet\\Events::ajax_dontAskAgainWorkingTime');
+								}
 							}, 'Do you want to start your working time?', 'Working time', {}, Et2Dialog.BUTTONS_YES_NO);
 						}
 						// overall timer running for more than 16 hours, ask to stop
diff --git a/timesheet/src/Events.php b/timesheet/src/Events.php
index a5c77af7b4..dbe2550b6f 100644
--- a/timesheet/src/Events.php
+++ b/timesheet/src/Events.php
@@ -194,6 +194,11 @@ class Events extends Api\Storage\Base
 		return $minutes;
 	}
 
+	/**
+	 * Name of session variable to not ask again if user denied starting working time
+	 */
+	const DONT_ASK_AGAIN_WORKING_TIME = 'dont-ask-again-working-time';
+
 	/**
 	 * Get state of timer
 	 *
@@ -208,6 +213,7 @@ class Events extends Api\Storage\Base
 					'start' => null,
 					'paused' => false,
 					'last' => null,
+					'dont_ask' => Api\Cache::getSession(__CLASS__, self::DONT_ASK_AGAIN_WORKING_TIME),
 				],
 				'specific' => [
 					'offset' => 0,
@@ -268,6 +274,16 @@ class Events extends Api\Storage\Base
 		}
 	}
 
+	/**
+	 * Remember for 18h to not ask again to start working time
+	 *
+	 * @return void
+	 */
+	static function ajax_dontAskAgainWorkingTime()
+	{
+		Api\Cache::setSession(__CLASS__, self::DONT_ASK_AGAIN_WORKING_TIME, true, 18*3600);
+	}
+
 	/**
 	 * Evaluate events
 	 *