How does CryptoKitty implement scheduling functions such as give birth function or auction ending function.

I tried to track it through Eth Fiddle but didn't find how it was done. Is there a function that calls itself every block mined and makes all the necessary checks whether the birth time or auction time is up?

I wanted to know because I wanted to do something similar, I want to create an auction and after a certain duration, the object would go to its highest bidder automatically.

I looked into Ethereum Alarm Clock but it seems a little unstable at the moment and doesn't seem to be live on main net either.

Thanks in advance.

2 Answers 2


Ethereum Alarm Clock is live on main net and stable. There was more than 1000 ETH moved through its protocol. It was also security audited.

Here is tutorial how to schedule transaction: https://medium.com/@MyCrypto/schedule-your-ethereum-transactions-now-on-mycrypto-92a6305f7dcc

It is integrated in MyCrypto (toggle 'Send Later').


In CryptoKitties, there is no scheduling of functions. Rather, the birth function or auctionended function must be manually called via a transaction.

How do kitties get born on schedule then? Cryptokitties depends on people to call the birth function in a transaction. They charge a .08 ETH mating fee to provide incentive and offset the gas costs of whoever is calling that birth function. AxiomZen also ran a birth daemon that watches the chain and then calls the birth function on kitties ready to be born.

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