I think you can easily find a lot of answer for that question. Please firstly make your search basically in the internet. You can use Google. It is so easy.

Please go www.google.com and make simple search in it.

For example I found this : https://www.investinblockchain.com/ethereum-constantinople-january-2019/
 
https://ethereumworldnews.com/ethereum-hard-fork-test-goes-awry-no-constantinople-in-2018-developer-says/

https://cointelegraph.com/news/ethereum-devs-reach-consensus-to-delay-constantinople-hard-fork-until-january-2019


See? it is so easy.