Hi, Hope I can give some ideas for research... - Did you consider this to be a localisation issue? What is your client (user) time zone, what is your server time zone? There might be an overlap so that you get evening results of 25 March and morning results of 26 March as 1 result. - In general, I noticed that as from version 3.0, date and time functions working easier & better. - I actually had some issues in the past that look a bit like yours, and that were due to localisation (check both attributes in your domain model: is "localize" having the same setting (yes/no). One way to trace Mendix localisation issues is to look at the raw data eg through Ms SQL Server client. If you store a same date time stamp in both attributes, do they get the same value in the db? - Have a look at this info, maybe it helps.
I don't recognize this issue immediately but I recommend upgrading to 3.x, we significantly improved datetime handling there. Also see https://world.mendix.com/display/refguide3/Date+and+Time+Handling+in+3.0