There is no exact time limitation or bindings for this. This depends on you how frequently you are publishing posts. Google also has a budget for this. And I think you know that there are millions of sites on Google. And Google has to crawl all of them. And it is related to the index. As soon as Google will crawl your blog it will get started indexing. So make regular posts or update your posts regularly and then Google will increase the budget of crawling for your site.  And then your posts will start indexing very quickly. Normally if your site is very new then it can take 10 to 15 days also to crawl or index.