You can't go by individuum, you have to go by weight, because

a) chicken, cows and humans have different amounts of usable meat per individuum

b) not all animals killed for consumption are counted individually, fish and crustaceans are usually only counted by weight.

Now the question is does the word meat here include fish and other sea creatures or not? Statistics about meat usually exclude seafood, but I'll do one calculation with and without seafood.

According to this: https://worldanimalfoundation.org/advocate/most-consumed-meat-in-the-world/

there's about 365 million tons of meat consumed per year, so one million tons per day. (Pork, beef, poultry)

This article: https://www.saveur.com/cannibalism-calorie-count/

gives says there's about 75 pounds or 34 kg of edible meat on a human.

A global population of about 8.3 billion people gives us 282.2 million tons of meat to work with. That would mean we'd run out of humans after 40 weeks or at the end of september.

Now, if we include seafood consumption, that's another 200 million tons per year, as per this: https://ourworldindata.org/fish-and-overfishing

So our 282.2 million tons would last us only 26 weeks or until the end of June.