drupal 7 date field stores todays date even when user hasnt entered a value I don't want it to! :-)

I'm using custom forms implementing a date field, then saving values manually to a node later. I could add an extra step preventing the value from being saved to the node, but I won't have the necessary info available to calculate whether to do this if it's an 'edit'.

Any ideas? I just dont want to save a value if the users doesnt enter anything. Seem's simple enough to me... :-S
By Form API reference you need to manually set '#default_value' to prevent it from defaulting to today. So just add: 

'#default_value' =&gt; NULL,


to your field's array to prevent it.