how long do i leave it before i report my cat missing

[MishyB]

Adopted a cat 3 weeks ago from blue cross and he had been kept in all that time. He went out at 6.30pm last night for the first time and hasn't been back since, despite me shaking treats, calling him etc. He is neutered and microchipped. When should I report him as missing or start panicking?

I would keep a look out and tell neighbours if you see them, but not panic yet. A cat I used to have regularly took off overnight at first. Longest I've ever had a cat missing was 12 days - he was found in a shed.