Very useful. Should add week and month interval to date calculator and it would be perfect.
Very handy for doing interval calculations and binary searches between dates. Very responsive developer.
Perfect for calculating global (ie 90 day) period for medical billing. Has a few ways of doing it. Nice easy to use interface for selecting dates.
Perfect for trial lawyer. Have to set trials w/i certain time frames
If you enter the last menstrual date or day of ovulation, it displays the expected date of birth and gestational age of schedule.