How to write and IF statement--comparing a column with date-time value with now() in Google Sheets?

I know if date value()

Like Column B has due dates. I need it to say if the date-time listed in Column B is less than now (past the due date), blablabla

So how do i represent the value of the date-time cell so I can compare it with B?

This works for JUST the date: datevalue(B:B)

but it needs to be date-time value and I can't find a function for that! I'm a newb, bear with me...