facing issue in coverting string to timestamp

Hi,

I am using a calculated attribute in a calculation view. In this calculated attribute, I am using a coversion function longdate() to convert a string to Timestamp. Please see snapshot 1 which shows the expression for calculated attribute. The corversion I am talking about is in the highlighted part(blue) in snapshot1.

Now I have used this same calculated attribute (with ofcourse, the same expression) in another calculation view succuessfully. But, in this calculation view, I am facing an issue if I include this calculated attribute. Although the view still activates after inclusion of this calculated attribute, but I get the following error on data preview (please see snapshot 2 for this error).

Any help regarding this will be appreciated ?

Thanks,

Aman