Summary

All‑day appointments in Dynamics 365 can display an incorrect date (typically one day earlier) when created around Daylight Saving Time (DST) transitions for certain time zones. This causes confusion for users and reduces trust in scheduling data, even though the underlying Dataverse data is stored correctly.

Problem Description

When users in DST‑affected time zones (for example, Sydney and Hobart – GMT+10 / GMT+11) create All‑Day Appointments, the appointment:

• Is stored correctly in Dataverse
• But is displayed as one day earlier in the model‑driven app form after DST ends

This behavior consistently occurs after DST rollover dates and can be reproduced in clean environments without customization.

From a user perspective:

• The appointment appears incorrect
• Users assume data corruption or system bugs
• Support cases are raised even though data integrity is intact

Expected Behavior

For All‑Day Appointments:

• The date shown in the UI should remain consistent with the user‑selected date
• DST or UTC conversion should not shift the calendar day
• The UI should treat all‑day events as date‑only, not date‑time during rendering

Actual Behavior

• All‑day appointments display one day earlier in the UI after DST changes
• This impacts multiple users in the same region
• Occurs without any customer customization

Affected Scenarios

• Time zones observing DST (e.g., AU Eastern)
• All‑day appointments only
• Model‑driven app forms
• Both newly created and viewed records after DST transition

Suggested Improvements

One or more of the following improvements would significantly reduce customer impact:

1. DST‑aware rendering logic for all‑day appointments in model‑driven forms
2. Treat all‑day appointments as true date‑only values at the UI layer
3. Provide a platform option or flag to disable DST conversion for all‑day events
4. Improve documentation or warnings if this behavior is by design

Customer Impact

• Impacts user trust in calendar and scheduling features
• Creates confusion and calendar inconsistencies

Business Justification

Fixing or improving this behavior would:

• Reduce support incidents related to DST
• Improve user confidence in Dynamics 365 scheduling
• Align UI behavior with user expectations for all‑day events
• Prevent repeated escalations each DST cycle