This is an example implementation of a custom Drupal views sort handler. See my blog post for more details.
It's meant to sort events in a way that shows users the most interesting events first:
- Future events come before past events
- Events closest to today come before events far in the past or future
Note that this is a sample of a custom module. The hook_views_data_alter() assumes the field name is field_event_date, but that's unlikely to be the right field for your site.
However, the sort handler is generic, so you could easily write a custom hook_views_data_alter() that applies it to a different field or property.