Hi Nihar,
I think you're talking about time buckets which is usually configured to decide the bucket strategy to shift the receipts and issues.Similarly, we do have an option for Forecast time bucket settings. Though I do not have practical working experience on this option, I think this would be correlated with the Forecast check that you decide to do against the Planned Independent Requirements ( PIRs ). You need to enable the Check against Forecast in Check Instructions tab. I think this would align the PIRs based on the shift hours that you maintain here and consume the same by the incoming demand elements.
You may want to take a look at the below post. It explains how Check against forecast works, but regarding the bucket strategy it is as same receipts and issues as explained above
http://scn.sap.com/thread/3436787
Hope I have been able to answer your question
Babu Kilari