Correct time dimensions of saved netCDF

From CST_SaveExp: Remaining issues (2).

When saving MD arrays to NetCDF in a single file, since the file has dimensions sdate and ftime, it is not possible to retrieve time values directly. The proposed time units are:

        double sdate(sdate) ;
                sdate:units = "hours since 2017-02-01" ;
                sdate:long_name = "sdate" ;
                sdate:sdates = "2017-02-01, 2018-02-01" ;
        double time(time) ;
                time:units = "months" ;
                time:long_name = "time" ;
                time:calendar = "proleptic_gregorian" ;