"every four weeks on Thursdays" needs a peg, a start date, on which to hang the counting. Of course, this peg will need to be updated when/if a call is moved a week or two (as opposed to skipped entirely).
It may be better to pick a particular Thursday of each month (nominally 12 meetings per year, if set to avoid holidays) than to use "every four weeks on Thursdays" (nominally 13 meetings per year), which will gradually climb from fourth to first.
"every four weeks on Thursdays" needs a peg, a start date, on which to hang the counting. Of course, this peg will need to be updated when/if a call is moved a week or two (as opposed to skipped entirely).
It may be better to pick a particular Thursday of each month (nominally 12 meetings per year, if set to avoid holidays) than to use "every four weeks on Thursdays" (nominally 13 meetings per year), which will gradually climb from fourth to first.