Some teams don't want clients to see internal schedule dates. The Hide dates from Clients setting stops client users from seeing start, due and completion dates for tasks, milestones and projects.
Who can change this: workspace admins. It's off by default.
Turn it on
Open Manage Workspace → Client Task Management.
Under Date visibility, turn on Hide dates from Clients.
What clients see when it's on
No Timeline tab on their projects.
No dates on tasks, milestones or the project Overview, and none in their emails or exports.
No date sorting or due-date filters.
Tasks clients create themselves keep their dates, because the client set those dates.
What your team sees
Nothing changes for vendor users. They always see every date. To preview what a client sees, use Client View on a project.