How to specify output file cell format when using ssconvert –merge-to create ODS file from multiple CSVs?

I successfully converted a series of .csv files into a single .ods spreadsheet file, but I had a minor formatting problem: all cells with date contents ended up with date and time format. Command used:

ssconvert --merge-to dir/output_file.ods dir/*.csv

Is there a way to tell ssconvert to use only date instead for those cells?

Thanks!