Create table using select statement Truncated incorrect datetime value:
From the looks of the error message, the UTC should not be part of the date. My guess is that date is not using the DATETIME or TIMESTAMP data type. It must be a string.

Try running it like this : 

Create table dummy_table AS
select Cust_ID User_Id , DATE_FORMAT(LEFT(`Date`,19),'%M %Y') DT
from result_table.user_signup_date;


The expression LEFT(Date,19) will drop off the everything after the timestamp.