Calendar: incorrect date shown in pop-up when using Russian locale.

In the Russian locale, the pop-up calendar does not display the correct date.

To reproduce:

1. Set Locale to Russian
2. Select a date (e.g. with month May) from pop-up calendar on a date field - e.g. Due Date
3. Click on calendar icon again to display pop-up calendar.
4. Note that the incorrect date is shown (normally the month June is displayed) in the pop-up and does not correspond to the previously selected date.

This appears to only occur for Russian locale.