I have a rule that sends an email out to subscribers on the 28th of each month. The rule is executed when cron is run, I have cron set to automatically run once a day.
I also use linkchecker, which uses cron to check the links on the site. Right now I have to remember on the 28th of the month not to run cron for the linkchecker, otherwise my subscribers will get multiple emails that day for each time cron was run.
How can I limit the rule to only run once in any specific day, so that I don't have the potential to accidentally run cron manually and spam my subscribers?