How to handle date data for Knn?
Can date data be used as a feature?


Yes.


  If so how do I handle them ?


Think about your problem. Why should the date be a reasonable indicator for the success of a startup? Answering this question tells you also in which way you need to transform it.

Most often, when I use some date information for models, I do the following:


Day of the week: integer/one-hot encoding for Monday, Tuesday, ..., Sunday
Month: integer/one-hot encoding for January, February, ..., December
Hour of the day: integer/one-hot encoding for 0, ..., 23
Seconds/minutes/hours/days since XY: Usually normalized or at least scaled in some way