diff --git a/README.md b/README.md
index 6169512..29e8e63 100644
--- a/README.md
+++ b/README.md
@@ -44,17 +44,17 @@ Title: Calendar
 Calendar: 
 -
   summary: My Event
-  _beginDate: 12/14/2014
-  _beginTime: 10:00
-  _endDate: 12/14/2014
-  _endTime: 15:00
+  _begin_date: 12/14/2014
+  _begin_time: 10:00
+  _end_date: 12/14/2014
+  _end_time: 15:00
 - 
   summary: My supercool event for the whole day
   description: This wil be a nice event!
-  _beginDate: 10/01/2014
+  _begin_date: 10/01/2014
 ```
 
-The `Calendar` field contains all events in a [YAML](http://getkirby.com/blog/structured-field-content) list. Each event has several own fields, too, but of them only  `_beginDate` is mandatory (see [event-fields](#event-fields)).  You can define as many other fields as you like.
+The `Calendar` field contains all events in a [YAML](http://getkirby.com/blog/structured-field-content) list. Each event has several own fields, too, but of them only  `_begin_date` is mandatory (see [event-fields](#event-fields)).  You can define as many other fields as you like.
 
 ### Calendar object
 
@@ -120,20 +120,20 @@ The locale is set by Kirby's language configuration. So if you've set up everyth
 
 Events can have arbitrary fields. However there are the special fields for this plugin marked by a `_`-prefix:
 
-- `_beginDate`: The only **mandatory** field specifying the date, the event begins.
-- `_beginTime`: The time of the day the event begins.
-- `_endDate`: The date the event ends.
-- `_endTime`: The time of the day the event ends.
+- `_begin_date`: The only **mandatory** field specifying the date, the event begins.
+- `_begin_time`: The time of the day the event begins.
+- `_end_date`: The date the event ends.
+- `_end_time`: The time of the day the event ends.
 
 The behavior with different combinations of these fields is the following:
 
-- only `_beginDate` given: The event lasts the whole day.
+- only `_begin_date` given: The event lasts the whole day.
 
-- `_beginDate` and `_beginTime` given: The event lasts from the given time until midnight (12 am) of the following day.
+- `_begin_date` and `_begin_time` given: The event lasts from the given time until midnight (12 am) of the following day.
 
-- `_beginDate` and `_endTime` given: The event lasts from midnight until the given time of the day.
+- `_begin_date` and `_end_time` given: The event lasts from midnight until the given time of the day.
 
-- `_beginDate` and `_endDate` given: The event lasts from mindnight of the beginning day until midnight of the day after the ending day.
+- `_begin_date` and `_end_date` given: The event lasts from mindnight of the beginning day until midnight of the day after the ending day.
 
 ## Functions
 
diff --git a/blueprints/calendar.php b/blueprints/calendar.php
index ad8bfda..a42c5bf 100644
--- a/blueprints/calendar.php
+++ b/blueprints/calendar.php
@@ -12,8 +12,8 @@
 		entry: >
 			<strong>{{summary}}</strong><br>
 			{{description}}<br>
-			Beginning: {{_beginDate}} {{_beginTime}}<br>
-			End: {{_endDate}} {{_endTime}}
+			Beginning: {{_begin_date}} {{_begin_time}}<br>
+			End: {{_end_date}} {{_end_time}}
 		fields:
 			summary:
 				label: Summary
@@ -22,19 +22,19 @@
 				label: Description
 				type: textarea
 				size: small
-			_beginDate:
+			_begin_date:
 				label: Beginning date
 				type: date
 				format: MM/DD/YYYY
-			_beginTime:
+			_begin_time:
 				label: Beginning time
 				type: time
 				interval: 15
-			_endDate:
+			_end_date:
 				label: Ending date
 				type: date
 				format: MM/DD/YYYY
-			_endTime:
+			_end_time:
 				label: Ending time
 				type: time
 				interval: 15
\ No newline at end of file
diff --git a/calendar/lib/Event.php b/calendar/lib/Event.php
index 7675a93..cd2956b 100644
--- a/calendar/lib/Event.php
+++ b/calendar/lib/Event.php
@@ -5,22 +5,22 @@ class Event {
 	/**
 	 * The string for the beginning date field key of an event.
 	 */
-	const beginDateKey = '_beginDate';
+	const beginDateKey = '_begin_date';
 
 	/**
 	 * The string for the beginning time field key of an event.
 	 */
-	const beginTimeKey = '_beginTime';
+	const beginTimeKey = '_begin_time';
 
 	/**
 	 * The string for the end date field key of an event.
 	 */
-	const endDateKey = '_endDate';
+	const endDateKey = '_end_date';
 
 	/**
 	 * The string for the end time field key of an event.
 	 */
-	const endTimeKey = '_endTime';
+	const endTimeKey = '_end_time';
 
 	/**
 	 * An array of field keys that are required to create an event.
@@ -66,7 +66,7 @@ class Event {
 
 	/**
 	 * @param array $event The fields of this event including the 'private'
-	 * fields which start with a <code>_</code> (e.g. <code>_beginDate</code>).
+	 * fields which start with a <code>_</code> (e.g. <code>_begin_date</code>).
 	 */
 	function __construct($event) {
 		self::validate($event);