[MidlifeFlyer]

I'm not sure what you are asking. Passenger currency is measured in "days." Instrument currency is measured in "calender months."

Like landing currency, however, instrument currency is a "lookback." Currency expires when you can no longer look back over the past 6 calendar month and not find 6 approaches, a hold (and the redundant interception and tracking).

So long as you understand the "calendar month" concept (forget the days altogether), you should be able to asnwer the question.