It is useful to produce monthly averaged datasets for diagnostics which compute time averaged quantities. Specifying a periodic ``interval'' for output and an averaging ``period'' as discussed in Section 38.4 is not helpful when months vary in length. However, enabling option monthly_averages will over-ride values specified by ``interval'' and ``period'' and produce monthly averaged datasets. However, this option is global and applies to all time averaged diagnostics that are enabled. The only caveat is that if the model is started or stopped at any time other than a month boundary, the first or last average will not be over the full month.