Here is a simple validator I wrote for to check that the input is a valid date, and is >= today.
If you want to use YYYY-MM-DD date formatting instead, just edit the string in line 6 to '%Y-%m-%d'. You will also want to change the error text on line 11.
1 import datetime, formencode
2
3 class DateTodayOrFuture(formencode.FancyValidator):
4 def _to_python(self, value, state):
5 try:
6 val = datetime.date.strptime(str(value), '%m/%d/%Y')
7 except ValueError:
8 val = None
9 if not val:
10 raise formencode.Invalid(\
11 'This date is invalid, it must be mm/dd/yyyy', value, state)
12 else:
13 if date(val.year, val.month, val.day) < datetime.date.today():
14 raise formencode.Invalid(\
15 'The date must be on or after today', value, state)
16 return value