The woman whose husband has died: is the mourning period calculated by months or by days?

The questioner:
He says: Honorable Shaykh, may Allah grant you success, does the woman who is in the state of mourning observe it by months or by days?

The Shaykh:
What is she in?

The questioner:
Mourning.

The Shaykh:
By months. Allah the Exalted said. I mean, do you mean by calculation or by the lunar months? She does not know the lunar months. If she knew the lunar months, she would observe the waiting period by the lunar months, but since she does not see the lunar months, she observes it by calculation: one hundred and thirty days, which is four months and ten days. Yes.