Altering mysql database column causes error in another column

First of all sorry everybody if this question sounds too basic.

I have a WordPress database and a table wp_comments.

In this table, I have two DATETIME fields, whose default value is 0000-00-00 00:00:00.

I need to change this value to CURRENT_TIMESTAMP, so for example I run the following query:

ALTER TABLE `wp_comments` MODIFY `comment_date` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP; 

So, comment_date (NOT comment_date_gmt) is the column to modify.

Now, when I run this query I get the following error:

Error 1067: Invalid default value for comment_date_gmt 

Why is this happening? What could I do?

[UPDATE]

This is the table:

CREATE TABLE `wp_comments` (   `comment_ID` bigint(20) UNSIGNED NOT NULL,   `comment_post_ID` bigint(20) UNSIGNED NOT NULL DEFAULT '0',   `comment_author` tinytext NOT NULL,   `comment_author_email` varchar(100) NOT NULL DEFAULT '',   `comment_author_url` varchar(200) NOT NULL DEFAULT '',   `comment_author_IP` varchar(100) NOT NULL DEFAULT '',   `comment_date` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',   `comment_date_gmt` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',   `comment_content` text NOT NULL,   `comment_karma` int(11) NOT NULL DEFAULT '0',   `comment_approved` varchar(20) NOT NULL DEFAULT '1',   `comment_agent` varchar(255) NOT NULL DEFAULT '',   `comment_type` varchar(20) NOT NULL DEFAULT 'comment',   `comment_parent` bigint(20) UNSIGNED NOT NULL DEFAULT '0',   `user_id` bigint(20) UNSIGNED NOT NULL DEFAULT '0' ) ENGINE=InnoDB DEFAULT CHARSET=utf8;  ALTER TABLE `wp_comments`   ADD PRIMARY KEY (`comment_ID`),   ADD KEY `comment_post_ID` (`comment_post_ID`),   ADD KEY `comment_approved_date_gmt` (`comment_approved`,`comment_date_gmt`),   ADD KEY `comment_date_gmt` (`comment_date_gmt`),   ADD KEY `comment_parent` (`comment_parent`),   ADD KEY `comment_author_email` (`comment_author_email`(10)); 

MySQL version is 5.7.33

[UPDATE]

I don’t know WHY but I know HOW I solved this issue:

ALTER TABLE `wp_comments` MODIFY `comment_date` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP, MODIFY `comment_date_gmt` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP 

This way, by modifying both fields together, I get no errors.

It works, but I’m still quite curious, so if have any idea to share… 🙂