Illustrative example. The dates and amounts below are provided for practice.
A test file with one ordinary annual birthday and one one-time event can reveal import problems before a larger calendar is copied.
Save a yearless birthday for May 6 with annual repeat and a one-time reunion for July 10, 2027. Select both in the exporter, choose Selected dates, and export ICS without alarms for the first test.
Inspect the two meanings
The file contains two events. The birthday has a yearly rule, while the one-time reunion does not. The birthday series begins at its next occurrence relative to the local export date, so check the file's actual start year rather than assuming it is 2027.
The reunion retains July 10, 2027 even if that date is in the past when exported.
Test the receiving application
Import into a separate calendar when possible. Check both all-day dates, the birthday's following occurrence, and the lack of a reunion repeat. Check for duplicate entries before importing the same file again.
From May 6 to July 10, 2027, the elapsed gap is 65 days.
A successful download is not proof of compatibility with every calendar client. Verify the application and account you intend to use.