“It is clear under these circumstances that a scientific treatment of the notebooks from Blomberg, Philippi, Hintz cannot be considered and used as units, like Schlapp  did, but rather they must first be dissected into their parts in order to disclose from the latter the true units underlying them and, when possible, to order these chronologically.”
“Es ist klar, daß unter disen Umständen eine wirklich wissenschaftliche Behandlungsweise die Hefte von Blomberg, Philippi, Hintz nicht, wie Schlapp  es tut, als Einheiten betrachten und benützen darf, sondern sie vielmehr zunächst in ihre Bestandteile zerlegen muß, um aus letzteren dann die zugrunde liegenden wahren Einheiten zu erschließen und diese nach Möglichkeit chronologisch zu ordnen.”
— Erich Adickes [1911a, 44]
We must be able to date the source lecture of the notes within some fairly narrow approximation, without which the notes are of little use, but doing this is rarely straight-forward.
For instance, a student might buy a set of lecture notes, then add a date on the title-page with the semester that he attended the lectures; here the date would correspond to any marginalia added, but not to the body of the notes (e.g., the Euchel anthropology notes). In this instance, we should be alerted to a possible problem with the date given on the title-page because the handwriting would be different from the rest of the page and the notes themselves; but the student could also borrow the set of notes and copy them out himself, putting the current date on the title page (or perhaps at the very end of the notes), such as we find with the Puttlich anthropology notes.
Or a student might copy material from an earlier set of notes into his own notes, such as the Dohna-Wundlacken anthropology notes, which mingle notes from 1772/73 and 1791/92.
Or a former student of Kant’s might purchase notes after he was finished with the course (or even after he left the university) as a record of what he learned or might have learned. Hermann Blomberg, for example, attended the university in the early 1760s, left his name (but not a date) on what are now the Blomberg logic notes — good circumstantial evidence that the source lecture of the notes was in the early 60s. Other evidence, however, shows that the source lecture was a decade later, and thus that Blomberg acquired the notes after he had already left the university.
These possibilities — and there are many more like them — should make us especially cautious when assigning a source lecture to a set of notes.
 Adickes was one of the first to call attention to these difficulties [1911a, 2-3].
Resources for Dating Notes. These include the published catalogs of lectures (which provide fairly good evidence of when Kant lectured on various topics), matriculation records of students, the paper itself, internal clues (e.g., references to some recent publication or event, or to a view Kant expressed in a publication, or whether a contemporary person is referred to in the past or present tense,) and stylometric analysis (e.g., noting the relative frequencies of certain words or phrases) that allows a dating of the texts relative to each other (this last method has been greatly enhanced by the work of Norbert Hinske and his colleagues at Trier).
The question of dating is always bound up with the question of how the notes were produced. We can use the above resources for dating a set of notes; but if those notes are composed from various textual or oral sources, then the dating of one passage obviously cannot be extended to all the notes of that set.
Also, when dating these notes we must distinguish the date of the source lecture (the lecture that some auditor attended and recorded in his notes) and the date when the notes themselves were prepared. These are often the same semester, but not always. The notes could have been prepared either concurrently with the source lecture or sometime after, and sometimes they were written at different times — for instance, the main body might be written at the time of the source lectures, with marginalia added years later, or perhaps even in the context of a later course of lectures, or a set of notes might be brought to a lecture (thus, with content from one or more previous source-lectures) and marginalia added from the current set of lectures. Particularly confounding are notes copied from two or more other sets of notes, thus with multiple source-lectures for the main body of the notes, with any marginalia stemming from a still later semester — and this was not at all uncommon.
Often exact dates are not possible, and the best that can be managed is a terminus post quem (or terminus a quo; the earliest possible date) and/or a terminus ante quem (or terminus ad quem; the latest possible date).
 Occasionally a watermark can be traced back to a certain paper mill whose production history might offer a terminus post quem for the preparation of the notes themselves. For instance, the Trutenau watermark is visible on several sets of notes (the an-Berlin anthropology and moral philosophy notes, the an-Pillau, physical geography notes, the Volckmann notes on physical geography and metaphysics, and the von Schön metaphysics notes), and this mill was producing writing paper of this sort no sooner than 1779, and was readily available only beginning in 1782 [Stark 1991b, 291].
 For instance, Gedike’s translation of Plato published in 1780 establishes a terminus post quem for the Hechsel logic notes; mention of water as elemental (rather than as compositional) suggests a source lecture prior to Kant having learned of Lavoisier’s work on oxygen, thus a terminus ante quem of 1785 for the an-Pölitz 1 metaphysics notes; and mention of the Academy prize essay question for 1780 (announced November 1777) provides a terminus post quem for sets of notes on philosophical encyclopedia (an-Friedländer 4.1), anthropology (Puttlich, an-Gotthold, and Reichel), and logic (Hechsel, an-Wien, an-Warszawa, and an-Jäsche).
 Brandt/Stark [1997, ciii-civ] warn us from too ready a reliance on this sort of evidence since the German present tense can be used indifferently between living and dead authors, but it may still have some use. Heinze [1894, 509], for instance, noticed that Crusius [bio] was mentioned in the past tense in the an-Pölitz 1 notes on metaphysics, leading him to date these to no earlier than WS 1775/76 (since Crusius died on October 18, 1775). The relevant passage is:
“Crusius had his head full of such wild fantasies, and he was quite happy that he could think such.” [AA 28:233]
“Crusius hat von solchen Schwärmereien den Kopf voll gehabt, und er war so glücklich, daß er sich so was ganz denken konnte.”
It is interesting that Crusius was also mentioned in the Philippi logic notes that are reliably dated to the SS 1772, and here he is referred to in the present tense:
“Crusius has an anti-philosophical method which undermines all philosophy. He advances things as subjective laws which are often only the effects of the understanding and not laws. He has sheer phantoms of the brain. He casts aside all means of proof.” [AA 24:335; see also 24:468]
“Crusius hat eine antiphilosophische Methode, die alle Philosophie zu Grunde richtet. Er giebt Dinge als subjective Gesetze an, die oft nur Wirkungen des Verstandes und nicht Gesetze sind. Er hat lauter Hirngespinste. Er wirfft alle Mittel der Prüfung weg.”
Decoding Written Dates. Many of the notes come with a written date on their title page or at the end of the notes, but these must always be viewed with caution. Assuming the date was not miswritten, they provide an initial terminus ante quem, but without further investigation, one should not assume that they indicate the source-lecture, as they might instead refer to when ...
• a copied set of notes was completed or begun.
The an-Pillau geography notes appear to be of this sort, since the closing date of March 1, 1784, would be inappropriate for a last day of the semester, and so is more likely when the copy was completed; similary with the an-Werner geography notes, which bears a “March 27, 1793” date — this is a Wednesday midway through the semester break.
The Puttlich geography notes are an especially misleading variant. The notes appear to date from SS 1785, which is also the semester that Puttlich attended the course, and “1785” appears in all the dates written on the manuscript. So far so good. The notes, however, originated from someone else, and were merely copied by Puttlich. The cover reads “written [nachgeschrieben] by Christian Friedrich Puttlich Königsberg begun the 12th of July 1785” — but the semester actually began on April 13 and the “July 12” date is when he began to copy the notes. Similarly, we find at the end: “Ended the 16th December 1785”, but this is when he finished his copying (the semester itself ended on September 17). Puttlich's diary is extant, from which we learned these details about what really was going on.
• Or when a text was purchased or received.
The Rosenhagen notes on metaphysics — the source lecture is c.1777-80, the written date is “5 June 1788”, and Rosenhagen matriculated just a month earlier. The an-Holstein-Beck geography notes are dated 1772/73, when Holstein-Beck heard the lectures and received the notes, the content of which stems from 1757-59.
• Or when a later user of the notes speculated was the date of the source-lecture.
This may have been what happened to the an-Pölitz 3.2 notes on metaphysics; the source lecture is c.1790, the written date (in a hand different from the notes themselves) is “1798” and then corrected to “1789”, perhaps by a user who realized that Kant was no longer lecturing in 1798.
Such dates written on the sets of notes occasionally reflect the date of the source-lecture, but often they do not.
Many notes come with no dates at all, although some of these, such as the various sets of notes written down by Herder, can be reliably dated, since we know they are his and when he attended Kant’s lectures — and perhaps most importantly, because they clearly are not the product of the notebook copying industry.
 For instance, of the twenty-three known sets of notes from the moral philosophy lectures, it has been shown that thirteen of these all stem from the same (now lost) set of notes, whose source lecture is sometime between WS 1774-75 and WS 1777-78. Seven of these have dates written on the title-page and/or at the end of the notes (six of the sets are without date), and none of these dates refer to the actual source lecture. The dates given are 19 Sep 1777 (Kaehler), 9 Sep 1780 (Kutzner), 12 Oct 1780 (Brauer 2), 11 Feb 1782 (an-Mrongovius), 19 Apr 1785 (Collins 2), 4 Apr 1789 (Brandt), and 1791 (an-Berlin 2).
Dating Marginalia. Any marginalia in the notes also enjoy an array of possibilities of source and date. The marginalia might be written ...
• by a later user composed independently of Kant’s actual lectures.
This appears to be the case with the an-Powalski notes on moral philosophy. Powalski attended the university, and may well have attended Kant’s lectures on moral philosophy, which were being offered every other year, but he acquired his set of notes years later after he had left the university and was working as a rector, and at which time he appears to have added marginalia.
• Or by an auditor of a later set of lectures.
The source-lecture of the main text of the Bauch logic notes is c.1770s; the notes themselves were copied out in 1789, and the marginalia have SS 1794 as their most plausible source-lecture. The source lecture for Collins notes on moral philosophy is sometime during 1774-77, but Collins used this notebook during WS 1784/85 and the annotations almost certainly come from that semester as well. See also the Wolter notes on physical geography and the Euchel notes on anthropology.
• Or they could be additions from the same semester as the main notes and written by the same student.
The Philippi notes on anthropology were written WS 1772/73 (Kant’s first semester lecturing on anthropology), they bear an “October 1772” date on the title page, and the notes and marginalia are all written in the same hand. The Vigilantius notes on moral philosophy, written by Vigilantius during WS 1793/94, include quite long marginalia that Krauß [1926, 90-94] conjectures stem from a fellow student’s notes on those days when Vigilantius might have missed class, or perhaps they come from a Repetition session on Saturday (although this is less likely for an older student like Vigilantius), or perhaps from private conversations with Kant (as Kant’s legal advisor, Vigilantius would have had such opportunities).
• Or they might have been copied from notes from an earlier set of lectures.
Mrongovius appears to have made use of an older set of notes (an-Mrongovius, from 1774-77), inserting it as marginalia into his own notes (Mrongovius 4.2, WS 1784/85) from Kant’s lectures on moral philosophy. The Volckmann notes on physical geography, written by him during SS 1785, include marginalia that appear to stem from the an-Barth notes.