Barb has a list of everyone's birthdays and social security numbers. However, in some episodes the birth years listed do not match the ages given for the characters. Nikki and Margene's birthdays are actually the birthdays of the actresses playing them. The birth year given for Barb would make her the same age as Nikki, but she is clearly portrayed as being about 10 years older.
The stoves and microwaves often don't show the time, as though they aren't plugged in.