Is there a way to turn off the postback or the day links altogether for the calendar control?

Use the DayRender event of the caledar control, and set the day item IsSelectable to false:

Private Sub calEndDate_DayRender(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.DayRenderEventArgs) Handles calEndDate.DayRender
    e.Day.IsSelectable = False
End Sub

Peter
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Work smarter, not harder.

That worked thanks.

Is there a way to handle, if IsSelectable is set to true, the day clicks? For example, if someone clicks a day it pops up a window with information on that day.

The .net Calendar control is a server control. If doesn't provide any native functionality for client side events. Add this to your DayRender handler:

e.Cell.Attributes.Add("onClick", String.Format("alert('{0}');", e.Day.Date))
e.Cell.Style.Add("cursor", "hand")

Modify the onclick client string to open your window.

Peter
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Work smarter, not harder.