Could we use everyday at the beginning of the sentence?

For example:
Everyday I sunbathed on the beach and swam in the warm sea.
Here's a usage note from the Oxford dictionary:
"The adjective everyday, 'pertaining to every day, ordinary,' is correctly spelled as one word ( : carrying out their everyday activities), but the adverbial phrase every day, meaning 'each day,' is always spelled as two words ( : it rained every day)".

Yes. But it is two separate words when used this way.

It's one word as an adjective,
eg my everyday sweater.

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Yes, but it's two words: "every day".
 JohnParis's reply was promoted to an answer.
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