Has the format for timestamps covering (say) a few hours changed? The following is still possible with "C-c .", but (I think) it is not documented in the Org-Mode manual:
<2021-11-27 Sat 10:30-12:30> This seems to be the new standard: <2021-11-27 Sat 10:30>--<2021-11-27 Sat 12:30> -- David Masterson
