nextcron.py reads one or more crontabs from stdin and displays upcoming cronjobs which are about to run next. It is written in pure Python 3 and needs no additional modules.
From its built-in help (nextcron.py -h):
nextcron.py -- displays upcoming cronjobs Usage: nextcron.py [<maxjobs>] [<isostart>] [+|-<startdelta>] nextcron.py [-h | --help] Synopsis: crontab -l | nextcron.py [<parameters> ...] nextcron.py [<parameters> ...] < /etc/crontab cat /var/cron/tabs/* | nextcron.py [<parameters> ...] Parameters: The order of parameters is irrelevant. You may add or omit them at your ease. <maxjobs> Display just next <maxjobs> upcoming cronjobs; default: 20 <isostart> Display jobs starting at <isostart> and later instead of now; valid examples of <isostart>: 2021-10-30 (Oct 30th, 2021) 2021-12-01 20:15 (quarter past 8 p.m. on Dec 1st, 2021) 2022-01-01 00:00:23 (23 seconds into 2022) +|-<startdelta> When displaying jobs, add or substract <startdelta> minutes to the start date and time, which may be now or <isostart>; default: 0 --version Display version number -h, --help Show this help ;-)