I think that gregorian_proleptic is not a standard name according to
https://www.unidata.ucar.edu/software/t ... eTime.html
Should be proleptic_gregorian
Seems semantic but ncview is picky and some other software as well.
Easy fix in Utility:
dateclock.F:809: calendar='proleptic_gregorian'
dateclock.F:827: calendar='proleptic_gregorian'
Cheers
Ivica