How to insert TIMESTAMP into my MySQL table?

In addition to checking your table setup to confirm that the field is set to NOT NULL with a default of CURRENT_TIMESTAMP, you can insert date/time values from PHP by writing them in a string format compatible with MySQL.

 $timestamp = date("Y-m-d H:i:s");

This will give you the current date and time in a string format that you can insert into MySQL.

Please try CURRENT_TIME() or now() functions

"INSERT INTO contactinfo (name, email, subject, date, comments)
VALUES ('$name', '$email', '$subject', NOW(), '$comments')"

OR

"INSERT INTO contactinfo (name, email, subject, date, comments)
VALUES ('$name', '$email', '$subject', CURRENT_TIME(), '$comments')"

OR you could try with PHP date function here:

$date = date("Y-m-d H:i:s");