Trade Date Vs. Settlement Date

There are two key dates involved in the transaction:

trade date: the date at which an agreement has been entered

settlement date: the date the transaction has been finalized

Do I own a stock as of the trade date or the settlement date?

It is the settlement date, however, that marks an official transfer of ownership from the seller to the buyer. While there may be differing rules for the various jurisdictions around the world, the general view is that ownership is transferred when the funds are given in exchange for the security, which happens on the settlement date.

When accrual interest starts from?

If the transaction involves interest, the interest cannot be recorded on the books until the settlement date has arrived.
you don't earn interest on stuff you haven't paid for. So the accrual starts from settlement date.

reference links:

http://www.investopedia.com/terms/t/tradedateaccounting.asp

http://www.investopedia.com/terms/s/settlementdateaccounting.asp

Who owns? (http://www.investopedia.com/ask/answers/06/settlementtradedate.asp)