I am using the latest version of ACT 4.5.7.123 & found a particular bug when changing years. Its really hard to repro the issue so ill be as thorough as possible. The bug can be reproduced in the "Default Calendar"(first one) & the "Calendar with an associated button"(Third one) available as demo here: [ACT Samples](http://www.asp.net/ajaxLibrary/AjaxControlToolkitSampleSite/Calendar/Calendar.aspx)
Or you can also, create a new project, add a textbox & a CalendarExtender.
```
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<ajaxToolkit:CalendarExtender ID="TextBox1_CalendarExtender" runat="server"
Enabled="True" TargetControlID="TextBox1">
</ajaxToolkit:CalendarExtender>
```
1.- Using your mouse only click on the "Month, year", to get to the month selection,
![Image](http://i.imgur.com/cPVSkG0.png?2)
2.- Then click on the year to get to the year selection.
![Image](http://i.imgur.com/Ag99Ujs.png?1)
3.- Click on "2012", click on April, then click on day 4
![Image](http://i.imgur.com/VHNZ0WI.png?1)
the current value should be "04/04/2012"
During this whole process you should only use your mouse, do __not__ type the date.
4.- remove your focus from the calendar and then click again on the "Month, year" at the top.
![Image](http://i.imgur.com/0OMV7OR.png)
5.- Click on the year, then on "2013"
![Image](http://i.imgur.com/hygzcdn.png)
__Result:__
The year selected is not "2013" it stays at "2012".
![Image](http://i.imgur.com/t4OJ4SH.png)
The issue seems to only happen when dealing with the current year and the previous one, changing to any other year makes the control behave normally again.
Comments: I have also come across this issue.
Or you can also, create a new project, add a textbox & a CalendarExtender.
```
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<ajaxToolkit:CalendarExtender ID="TextBox1_CalendarExtender" runat="server"
Enabled="True" TargetControlID="TextBox1">
</ajaxToolkit:CalendarExtender>
```
1.- Using your mouse only click on the "Month, year", to get to the month selection,
![Image](http://i.imgur.com/cPVSkG0.png?2)
2.- Then click on the year to get to the year selection.
![Image](http://i.imgur.com/Ag99Ujs.png?1)
3.- Click on "2012", click on April, then click on day 4
![Image](http://i.imgur.com/VHNZ0WI.png?1)
the current value should be "04/04/2012"
During this whole process you should only use your mouse, do __not__ type the date.
4.- remove your focus from the calendar and then click again on the "Month, year" at the top.
![Image](http://i.imgur.com/0OMV7OR.png)
5.- Click on the year, then on "2013"
![Image](http://i.imgur.com/hygzcdn.png)
__Result:__
The year selected is not "2013" it stays at "2012".
![Image](http://i.imgur.com/t4OJ4SH.png)
The issue seems to only happen when dealing with the current year and the previous one, changing to any other year makes the control behave normally again.
Comments: I have also come across this issue.