FISA warrants: why are the dates still redacted?

Question

In July, the DoJ released 412 pages of heavily redacted documents related to the FISA court's approval of surveillance of Carter Page, a U.S. citizen. The redactions, have become controversial.

Among the items redacted include the seemingly innocuous details like date(s) and specific citation to sections of the U.S. code authorizing this action. The coding of those specific redactions seems to indicate that the information is classified for national security or foreign relations reasons, prohibited from disclosure by law, and could reasonably be expected to interfere with enforcement proceedings.

Has anyone offer an explanation as to how that specific date of the application and U.S. code section citation are so secret?

Beside the above "simple" information, other redactions seem to be annotated with excessively complex notes. Can anyone decode the hyphenated FOIA exemptions annotations such as "b7E-1,2,3,7"? While the wording of 5 USC 552 (b) amounts to a single run-on sentence, (b)7E gets specific enough to narrow this down to just 34 words, that seem insufficient to explain references to sub-parts as high as 7.

DoJ's policy on exemption 7(E) is massive, and make reference to dozens of court cases, but does not itself seem to be subdivided to a point where identify the meaning of the "b7E-1,2,3,7".

Answer 1

The first dates I saw that were redacted were the "Declassify On:" dates, which is the set time in the future when the document in full must be declassified unless a waiver is sought. By default, this is 10 years after origination of the document (let's say we write a document on date of this answers' post, 10/16/18. By default, we can classify this until 10/16/28), however, this can be advanced to 25 years by any agency for any number of reasons. At the 25 year mark (10/16/43), the document is automatically reviewed and must be declassified unless it meets any one of nine specific exemptions.). At 50 years (10/16/68), it can remain classified for any one of two specific exemptions. At 75 years, it can only remain classified with special permission.

The reason why the declassification date would be redacted is that knowing when the date is set can hint to the nature of the redacted information. I'm not sure what other dates are redacted, as legal documents do not use hard dates ("On or about [insert date]" is preferred to avoid perjury) but if you have more, let me know, as it could be for another reason altogether.

Answer 2

In an earlier answer to this question [now deleted], a low-profile stack exchange member suggested the redaction of dates was done to conceal [from the public] how little time and effort the Foreign Intelligence Surveillance Court (FISC) puts into approval of surveillance requests against american citizens. Evidence supporting this conclusion seems confirmed. As of December 11, 2019, the DOJ posted an updated version of the Inspector General's report on the four FISA warrant applications which removed the redaction from many (if not all) of the dates I was questioning. This is noted in a cover-note explaining the update saying:

On pages ix, 164, 165, 214, and 364 we removed redactions of certain information related to Person 1. We also removed redactions throughout the report related to the dates the Carter Page FISA applications were filed and the dates FISA authority expired for each application. These changes to previously-redacted text were made in response to subsequent decisions made by the Department of Justice and the FBI about the classification of the underlying information. See page 14, footnote 24.

[Emphasis added]

While no explanation was provided as to why the dates had earlier been redacted, it can be seen, for example that on October 21, the NSD submitted the first (approved) application for a warrant (page 5). On the same day, the FISC order approving intrusive surveillance was approved the same day the warrant was approved (page iii).