My wonderful Dentist has had this wonderful form of calendar for a decade. He has moved to acquire latest equipments for surgery, x-ray but refused to adopt a simple effective system like Practo(congratulations for mention in economist) which his other colleagues are using.
Dentist gave me many reasons
– easy for receptionist/him to take a pencil/eraser and modify
– use both sides of very small piece of paper for the day
– easily put up time/procedure – also providing inputs for inventory
– green – less power consumption than device/internet charges etc
– controls his own data – very crucial for him