Because you might want to be stopped when trying to post a GL entry that will affect a FACTS pool for a cycle that is reconciled and closed, you can set a a System Option to result in either a warning or an error.   A warning will allow you to post, but an error will not.

To change the option, select Tools > System Utilities > System Options > GL > Warning_FACTS_Posted_for_Apply_Date.  Select Yes or None to generate a warning or NO to generate an Error.

If you have set the option to No, but you determine that there will be no harm in posting (e.g. you adjusted an historic gift to change the donor, which will not affect the FACTS pool), you can change the option to Yes, post the entry, then change it back to No after posting.  Alternately, if there are not too many journals to post you can navigate to the Journal Entry tab and enter in a FACTS confirm date value in the unposted journal:

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Frequently you create a large set of journals and forget to change the FACTS confirm date during creation ( asset rebalancing entries and administrative fees are two common examples).  In each of these, the apply date perhaps is the last day of the cycle, but the confirm date should have been the first day of the next.  You would typically change the system option to a warning, post the entries, change the option back and also go run the File Maintenance > FACTS > Change Confirm Date utility to move the confirm date into an open cycle