The date the court use to assess financial positio

Can anyone help tell me at what point does the court use to assess the monies each party hold?

Is it the day of separation?
The date of form E?
The date of First Direction Hearing?
The Day of Necree Nisi?

It's the date of the Form E, which can even be after the Decree Absolute (though not usually).

Of course, if there have been any underhanded financial activities between separation and the Form E, then it's a matter of proving that, and if there is a risk of major asset shedding, a court can issue an emergency order to prevent this.

If your ex was a millionaire, say, having made money through stocks and shares as their primary occupation, and you left it a year before the Form E and in that time they had lost two-thirds of it through trading, then the courts won't consider that as asset disposal unless you had evidence that it really was deliberate. If your ex had sold a house, or car or shares for way below market value, especially in some fashion that meant they could regain the use of them in future, then that would be asset disposal and the courts take a dim view of that.