offseting date by integer

Question

I've got a content type with fields: starting date: Date (Unix timestamp) duration: integer ending date: Date (Unix timestamp)

User is setting only starting date (year, month, day) and duration (in days) end after saving the content I would like to automatically calculate ending date (=starting date + duration)

I suppose I should use rules. I tried using actions like set value or calculate value but I failed. Could you help me?

Answer 1

Interval module may help you. It provides an interval field type and also a rules action: "Apply an interval to a date".

Answer 2

For a quick fix I would recommend making a simple custom module with this function:

function YOUR_MODULE_node_presave($node) {
  if($node->type === "your_content_type") { // Replace with the content type of your node.
    // Replace $node->XXX with the actual names of your fields.
    $startdate = $node->start_date[LANGUAGE_NONE][0]['value'];
    $duration = $node->duration[LANGUAGE_NONE][0]['value'];
    $enddate = &$node->end_date[LANGUAGE_NONE][0]['value'];

    $enddate = strtotime('+ ' . $duration . ' days', $startdate);
  }
}