Hi Frank,

This is little bug on our side. Please find this file

../wp-content/plugins/wpdatatables/source/class.datetime.wpdatacolumn.php

and in it around line 42

$timestamp = is_int( $content ) ? $content : strtotime( str_replace('/', '-', $content ) );

and change it to

$timestamp = filter_var( $content, FILTER_VALIDATE_INT ) ? $content : strtotime( str_replace('/', '-', $content ) );

Thank you for reporting this. We will include solution for this problem in next version of our plugin.

Hi Frank,
Thank you for your purchase.

Miljko is currently on vacation so I will try to help you. 
There are some reserved words from Wordpress and MySQL for column names and it can be very tricky to found the source of the issue.
Here you can take a look which of the words are reserved - Link.

Can you please provide me temporary WP admin credentials so I can take a look at your table. 
You can write credentials here but please check the Private replay so nobody can see it except us.

Hi Frank,

Thank you for reporting this.
We will release the update again and it will be on codecanyon in 2-3 days.

Please find this file

../wp-content/plugins/wpdatatables/source/class.datetime.wpdatacolumn.php

and in it around line 42

$timestamp = is_int( $content ) ? $content : strtotime( str_replace('/', '-', $content ) );

and change it to 

$timestamp = is_numeric( $content ) ? $content : strtotime( str_replace('/', '-', $content ) );

Hi Frank,

Please provide me a temporary WP-admin login for your site I will need it to investigate this.

You can write credentials here just check Private Reply so nobody can see them except us.