I not sure I get exact where you run in to problems, so if the following is not helpful please provide more details on the problem sympthoms that you observe.
In genral it is always better to solve formatting issues in the script, since then you get simpler expressions in the application front end, and also only use process for formatting during reloads.
Keep in mind that when working with dual values like dates, you might need to run both Date() and Date#() in order to set both the numeric value and the textual presentation.
After you have formatted the date value properly, and want to use it for further operations a preceeding load setup is a easy way to rework or use the value. See my calendar application as an example of preceeding loads;