Create a time span field The date module provides a handy widget for specifying a date.  Is there something similar on Drupal 6 for specifying a length of time such as 6 months or 3 days?  The time span will need to be converted to or stored as seconds for use by my module.
The Interval Field module looks like it would do the trick.

Interval field gives you a simple field and widget to allow users to enter interval values eg

2 months
3 days
4 years