Is the waiting period for a woman whose husband has died calculated by months or by a count of 130 days?

Question:
He says: Honorable Shaykh, may Allah grant you success. The waiting period for a woman whose husband has died is four months and ten days. It is known that some months are twenty-nine days. So do we calculate by months or by days?

Answer:
We do not calculate by months unless we see the new moon in every month; then we calculate by the new moons. But as long as we do not see the new moons, the count is necessary. The waiting period must be by the number, one hundred and thirty days. Yes.