Checking the weather of the day is important when choosing a suitable outfit. If by the end of the day it is going to rain, the shoes chosen will be based on this. Some people check the weather the night before, others every morning.
The occasion will define how far in advance the outfit will be planned. For instance, a birthday party requires something more fun that might already be in her wardrobe, whilst a wedding is an opportunity to buy something new.
Not directly related to an occasion, the diary refers to what the person has planned for everyday situations, such as meetings, gym classes, happy hours and company events.