fix #448 The calendar may have some issues depending on the timezone it is used

To avoid the issue, the new dates are created at noon.

For instance, the Brazilia timezone change the daylight saving time at midnight.
In javascript, a date created with new Date(year, month, day) at calendar change will result to the day before,
and the calendar widget will have repetitive days around this time.

Setting the dates at noon will prevent the day change.