Here is the stack trace that is printed to the page.

( ! ) Notice: Undefined offset: 1 in /Users/vayu/Sites/example.dev/wp-includes/post.php on line 1336
Call Stack
#	Time	Memory	Function	Location
1	0.0093	509688	{main}( )	../index.php:0
2	0.0094	512472	require( '/Users/vayu/Sites/example.dev/wp-blog-header.php' )	../index.php:17
3	0.0099	529376	require_once( '/Users/vayu/Sites/example.dev/wp-load.php' )	../wp-blog-header.php:13
4	0.0101	546832	require_once( '/Users/vayu/Sites/example.dev/wp-config.php' )	../wp-load.php:37
5	0.0114	648528	require_once( '/Users/vayu/Sites/example.dev/wp-settings.php' )	../wp-config.php:112
6	1.5505	45825904	do_action( )	../wp-settings.php:393
7	2.7630	48002344	call_user_func_array:{/Users/vayu/Sites/example.dev/wp-includes/plugin.php:525} ( )	../plugin.php:525
8	2.7630	48002424	Piklist_CPT::init( )	../plugin.php:525
9	2.7702	48041304	Piklist_CPT::register_post_types( )	../class-piklist-cpt.php:107
10	2.7738	48082680	register_post_type( )	../class-piklist-cpt.php:167
11	2.7738	48090680	get_post_type_capabilities( )	../post.php:1096

Great, that nice! 🙂

Okay, I activated the demos. I then added a new piklist demo post. The same problem appears there. But I am confused. On this page, it says that there must be a draft status, that you can relabel. However, the demo does not use the draft status.

Creating Custom Post Statuses

So when I want to save new piklist demo, then the status does not change and stays on the status “New”.

The same issue also happens on the button. The text has changed to “Save” and it does not say “Publish” like it does normally.

Thanks again for helping me out! I found the cause for my problem, and it’s because I had added this code:
https://piklist.com/support/topic/advice-for-sorting-by-date-with-date-picker/#post-4640, which by default does not let me use an empty value.
I do apologise for having wasted your time, but your help got me on the right track.
Thanks again!

Thanks Steve, but I had already tried this.

This is my code:

piklist( 'field', array(
	'type' => 'datepicker',
	'scope' => 'post_meta',
	'field' => 'invoice_approved_date',
	'value' => null,
	'label' => 'Dato godkendt',
	'attributes' => array(
		'class' => 'select invoice-approved-date',
		'placeholder' => 'Dato godkendt',
	),
	'options' => array(
		'dateFormat' => 'd-m-yy',
		'firstDay' => 1,
		'closeText' => 'Luk',
		'prevText' => 'Forrige',
		'nextText' => 'Næste',
		'monthNames' => ['Januar','Februar','Marts','April','Maj','Juni','Juli','August','September','Oktober','November','December'],
		'monthNamesShort' => ['Jan','Feb','Mar','Apr','Maj','Jun','Jul','Aug','Sep','Okt','Nov','Dec'],
		'dayNames' => ['Søndag','Mandag','Tirsdag','Onsdag','Torsdag','Fredag','Lørdag'],
		'dayNamesShort' => ['Søn','Man','Tir','Ons','Tor','Fre','Lør'],
		'dayNamesMin' => ['Sø','Ma','Ti','On','To','Fr','Lø'],
		'weekHeader' => 'Uge',
		'isRTL' => false,
		'showMonthAfterYear' => false,
		'yearSuffix' => ''
	)
) );

Okay thanks. Maybe I just don’t really understand the options parameter. Is this only for jQuery options?

Thanks, I did google it as well and tried several things, but actually I meant for Piklist options, not specifically for datepicker. There is no information about being able to use these options in the Piklist docs.

Thanks! 🙂