How to create dynamice date field?

[crmspace]

Hi,
if the calculated value should be shown before the users saves the task, you could create a javascript listener using the editviewdefs:

'includes' => 
      array (
        0 => 
        array (
          'file' => 'your/subfolder/path/myscript.js',
        ),
      ),

if the value should be calculated from the backend (so that users cannot change it after the js ran), logic hooks can be used:

Logic Hooks

It could also be possible using workflows, I didn’t check yet.
Edit: yes, workflows have a proper method to add minutes: