Currently KVRocks only supports integers and * in crontab format. I thought it would be nice to add support for the */n interval syntax. I understand that we can already add multiple crontab entries for the same feature like this:

bgsave-cron 0 3 * * * 0 6 * * * (and more...)

But it would be convenient if we could do something like this instead:

bgsave-cron 0 */3 * * *

Again, I'm new to C++ so no offense taken if the code provided is not good at all for your standards. The "month" part was a pain to do and I'm not sure about it. I used https://crontab.guru/#0_*_*_*/4_* to calibrate my code/tests for this.