diff --git a/docs/guide/output-formatter.md b/docs/guide/output-formatter.md
index 8dd03262e4..3c63a53117 100644
--- a/docs/guide/output-formatter.md
+++ b/docs/guide/output-formatter.md
@@ -124,6 +124,13 @@ echo Yii::$app->formatter->asTime('2014-10-06 12:41:00'); // 14:41:00
echo Yii::$app->formatter->asTime('2014-10-06 14:41:00 CEST'); // 14:41:00
```
+> Note: As time zones are subject to rules made by the governments around the world and may change frequently, it is
+> likely that you do not have the latest information in the time zone database installed on your system.
+> You may refer to the [ICU manual](http://userguide.icu-project.org/datetime/timezone#TOC-Updating-the-Time-Zone-Data)
+> for details on updating the time zone database.
+> See also: [Setting up your PHP environment for internationalization](tutorial-i18n.md#setup-environment).
+
+
Formatting Numbers
------------------
diff --git a/docs/guide/tutorial-i18n.md b/docs/guide/tutorial-i18n.md
index d56f33fa36..2e4cf8f119 100644
--- a/docs/guide/tutorial-i18n.md
+++ b/docs/guide/tutorial-i18n.md
@@ -523,3 +523,8 @@ We recommend an ICU version greater or equal to version ICU 49 to be able to use
One major feature that is missing in Versions below 49 is the `#` placeholder in plural rules.
See for a list of available ICU versions. Note that the version numbering has changed after the
4.8 release so that the first digits are now merged: the sequence is ICU 4.8, ICU 49, ICU 50.
+
+Additionally the information in the time zone database shipped with the ICU library may be outdated. Please refer
+to the [ICU manual](http://userguide.icu-project.org/datetime/timezone#TOC-Updating-the-Time-Zone-Data) for details
+on updating the time zone database. While for output formatting the ICU timezone database is used, the time zone database
+used by PHP may be relevant too. You can update it by installing the latest version of the [pecl package `timezonedb`](http://pecl.php.net/package/timezonedb).