A Known Day

S 15:38  To the day of the known time.

Known to whom? Did Iblis know? Does Satan know the Hour?

S 26:38 So the magicians were gathered for an appointment of a known day.

It would seem likely that the Egyptian magicians knew when to meet.

S 26:155 He said: This is a cow camel. She has a drink and you have a drink, a known day.

The Jalalayn:

He said ‘This is a she-camel; she shall drink a share of the water and you shall drink each on a known day.

The Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs:

(He said) Salih said to them: ((Behold) this she-camel) she is a sign that I am sent as a prophet to you. (She hath the right to drink (at the well)) one day, (and ye have the right to drink) another day, ((each) on an appointed day) i.e. in alternate days: one day for you and one day for her. altafsir.com

Drinking on alternate days?

S 38:81 To the day of the known time.

Is the known time known to Satan? Why does he not ask: 'What's that?' ? Does he already know of the Hour?

S 56:50 Are gathered for the appointed time of a known day.

Known to whom? Allah? If Allah.appointed it, wouldn't it know about it?