I have a job runs once weekly and also once at the end of each month. Becuase they are the same job, I just added two schedulings within the job. However when I forced to run the jobs to test ( by changing the date/time via the 'Control Panel'), it seems that the second schedule didn't get run, as it doesn't apprea in either the job history, in the 'Last Run Status(Start Date)', nor the 'Next Run Date'.
I know that I can simply add another job and schedule it once of a month. But I thought that defining them in one job is easy to manage as they are the same job.