Setting targets for ANN

The machine learning part of Matlab is quite new to me and I have looked at the examples given which seem to make sense.

However, for my application, I am wanting to see if there are relationships between seasonal weather data and a date at which an event (such as flowering) happens in a plant. So the input data would be various weather data such as weekly average maximum and minimum temperatures, rainfall, evaporation etc each year leading up to the event - flowering, which occurs on a given date for a particular year. This particular date would be the target I assume.

I am unsure how I might set up the input matrix and how I can incorporate a date as a target?

Kind regards, Wendy