iCalculator is intended to make explicit the dates defined implicitly in an icalendar file as per RFC5545 (RDATE, RRULE, EXDATE, ...). The outcome is conditionned to a given time window.
1-annum.com aims at synchronising lives, unfortunately the icalendar standard is a jungle of partial implementation and relative interpretation
of the standard.
Towards driving for greater interoperability this tool is provided free of charge as much as google app engine allows to help drive interoperability
of services based on the RFC5545 (with regards to RRULE, RDATE, EXDATE interpretations).