Problem with "last dates"

[MartinMilata]

Scenario

1. In time 14:00 I will do render of DateTimeButtonRange where I will set min 13:00, max 14:00, selected from, and selected to, and callback
2. User will 10min do nothing on page - no refresh, no render of DateTimeButtonRange
3. After 10min user will open picker
   
   and will click on last button 15min (it does not matter which)
4. Datetime is counted from max 14:00 (which was set in render before 10min) - 15min = 13:45, but current time is 14:10 - 15min = 13:55
5. I need to set max to current datetime - it is needed to do it when user open picker in point 3.