'Adds another instance of this category into the active_days counter.
We automatically count the event towards all relevant active_days. For
example, if the category "Windows" was seen 8 days ago it will be counted
towards the 30 day active, 14 day active but not against the 7 and 1 day
actives.
Args:
category: The category name to account this instance against.
label: Client label to which this should be applied.
age: When this instance occurred.'

def Add(self, category, label, age):

    now = rdfvalue.RDFDatetime.Now()
    category = utils.SmartUnicode(category)
    for active_time in self.active_days:
        self.categories[active_time].setdefault(label, {})
        if ((now - age).seconds < (((active_time * 24) * 60) * 60)):
            self.categories[active_time][label][category] = (self.categories[active_time][label].get(category, 0) + 1)
