Why is my inbox arranged differently from my Outlook program on my desktop?

And how can I change it to show everything by calendar date?

In OWA 2010, emails are sorted in conversations by default. Conversations collect all email with the same subject into one thread to allow easy reference to past messages and keep your inbox organized by subject.

To stop viewing conversation view in your inbox:

1. Click Conversations by Date.
2. Click Conversation in the drop-down menu. This will uncheck the box next to conversation and remove the conversation view groupings from your inbox.