How do I sort two different date content-types in a view? I have a view that filters two content-types (single event, and serial event) by date. The content-types have their own date-field (one with, one without date-repeat option). 

The view shows all the "serial events" first, and afterwards the "single events".

How can I change this order?

Is it because I use two different date-fields? 

The sort criteria are the following: 


Format
Format: Unformatted list | Settings
Show: Fields | Settings
Fields
Content: single event
Content: serial event  
Filter criteria
Content: Published (Yes)  AND Content: Category (exposed) | Settings AND Content: Type (in single event, serial event)  OR Date: Date (node) (Content: single event (field_serialevent) 
OR Content: serial event (field_singleevent) >= now)


I am using Drupal 7.14, with the latest versions development snapshots of the Views, Calendar,  and Date API modules.
Are you sure you are only have one sort field? It sounds like you are also sorting on "Type". If you are sorting on type, make sure the "Date" is the first in the sort fields. The order of the sort fields, makes the top ones dominant.