Getting the correct format_interval() in a node

I'm guessing you're trying to use format_interval() on the formatted output of the date instead of the raw date value. I am adding a new formatter, 'plain', which will be the raw db value, so you should be able to do something like:

print format_interval(content_format('mydate', $node->mydate[0], 'plain'));

The 'plain' formatter is not there yet, that will get added in later today.

I ended up doing this differently. I just committed a fix to add a format_interval formatter and a timestamp formatter. The format_interval formatter runs the date through a theme_date_format_interval() to format the results (and you can override the theme), or you can use content_format and the 'timestamp' formatter to return the raw timestamp and apply format_interval yourself. Or you can get any part of the date object and apply format_interval to it. Everything is explained in the descriptions for the various functions in date.module.