enter no end date for an event?

For birthdays and similar all‑day events, Outlook already treats them as having no end date in the sense that they are single‑day events that recur annually, not events with a finish time.

To create a birthday with no explicit end date:

1. Create or edit a contact and enter the date in the Birthday field.
2. Outlook automatically adds a yearly recurring all‑day event to the Birthdays calendar. There is no separate “end date” to fill in for this birthday series; it repeats every year.

If the Birthdays calendar view is not needed, it can be hidden or deleted without removing the birthday information stored on the contact.

References:

• Add a birthday calendar and reminder in Outlook
• Use a screen reader to add an appointment in Outlook
• You cannot disable the "No end date" option for appointments, meeting requests, tasks, or task requests in Outlook 2007