Hi Ho Dung,
If you are seeing a date different in UI, then it might be because you have set the Localized option to yes for your Date time Attribute.
Another thing you have to note is that, in Mendix, the datetime attribute value is stored in UTC format.
For example: The time component of a date selected from the date picker will always be the start of the day, which is 00:00, so in my database the value is stored in UTC format, which is based on where the application is hosted.
I hope this will help you. ATB!!
thanks so much