I'm trying to convert date and time to text but when I use this formula
=concatenate(text(A2,"yyyy-mm-dd")&" "&text(B2,"hh:mm:ss"))
the result is "true" and "false"
I tried to look my old file, and the result should look like this
Why are you even doing this?
In Excel, dates are stored as integers, while times are stored as decimals. As both are numbers, you can get a datetime (date AND time) by simply adding both values.
So, this formula should give you what you need:
=TEXT(A2+B2,"yyyy-mm-dd hh:mm:ss")
Result: