When releasing earnings, how/when is the “outstanding shares” part of the EPS calculation determined?

I can’t seem to wrap my head around this…So I understand that EPS is calculated by taking a company’s net income and dividing it by the number of shares outstanding. But at what point is the number of shares outstanding determined for the calculation?

For example like today when Alibaba released their Q4 Earnings, what date/time determines the outstanding shares for the EPS? Is the last day of Q4, the current number, or something else?