Meaning of "Day in day out"

[Salman]

Test No. incompl/inter-38 "Save the Day", question 5

It just didn't stop raining throughout our holiday, day in day ..........

(a) over
(b) under
(c) up
(d) out

Test No. incompl/inter-38 "Save the Day", answer 5

It just didn't stop raining throughout our holiday, day in day out.

Correct answer: (d) out

Your answer was: incorrect
It just didn't stop raining throughout our holiday, day in day over.
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what means "day in day out"

Salman

[Alan]

This means every day without stopping.
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English as a Second Language
You can read my ESL story Present Simple

[Torsten]

Exactly. There was a famous song by David Bowie called Day in Day out.

TOEIC listening, photographs: A city skyline