Hi,
this has nothing to do with your calculation directly.
The difference between the dateformat in your calculated notes overview and the query is caused by the webaccess platform.
If you look at the asp.net globalization culture setting within IIS you will see that the culture for webaccess is set to English en-US which causes the date to be shown as MM/DD/YYYY with am/pm time format.
The date in your calculation is generated by the application in the background, where I assume, that the setting invariante language is pulled and the date format reflects the regional setting of the windows server. And if this setting is en-GB you will get a date in the format DD/MM/YYYY.and 24h time format.
The time difference in the query result and you calculation result may be cause by your user time zone setting as all datetime attributes are stored in UTC datetime and will be shown in your local time zone set within the application.
Hope that everything is correct what I explained and understandable.
Regards
Fabian