30 day months in calendar

[a.larkin@xxxxxxxx]

Hello, I hope this isn't a stupid question...

I plot data from the UK met offices Unified Model (UM) using Ferret, and the data from the UM has 360 days in a year, with each month having 30 days. My problem is that Ferret has the correct number of days, hence my calendar gets out of sink. I know I can do 'cancel mode calendar' to see my data in days, but I really need to plot time series that have the time axis in months. How can I make Ferret do this?
Alice Larkin