Several dating systems were used on Pern throughout its history. While the early colonists recorded dates by counting the years that had passed since they had arrived on Pern, as time went on, Pern's history was recorded by counting how many years had passed since the beginning of the Pass or Interval. Hence, 259 AL becomes the Second Year of the Second Pass.

  • After Landing: 2508AL
  • Pass/Interval: (Day).(Month).1 - First Year of the Ninth Pass.
  • AIVAS Adjusted Turn: 2521AL

"After Landing" and the Pass/Interval System

The original dating method used on Pern was measured from the date of the "Landing" on Pern. As such, the suffix "After Landing" or "AL" was used to measure the years. At some point in time following the Third Pass, the "AL" suffix was dropped; likely a result of the original meaning being lost.

Following the "arrival" of Thread in 8AL, the Pass/Interval System was developed; years were grouped into fifty year "Passes"; when the Red Star caused Thread to land on Pern, or two hundred year "Intervals", when the Red Star's orbit took it away from Pern. These calculations were in fact flawed - the Red Star's orbit was unstable, and as such the length of a full cycle varied (see below for details).

As time went on, Pernese archivists began recording the years by counting how many years had passed since the Pass or Interval began, which resulted in the "true date" being lost. When AIVAS was rediscovered in the Ninth Pass, it was revealed that a total of thirteen years had been "lost" as the result of this; the year 2508AL was really 2521AL. The "true dates" were restored by AIVAS, and the new system dubbed the "AIVAS Adjusted Turn".

This system was inherently flawed, due to the fact that the Red Star's orbit was inconsistent. While it was generally believed that the Red Star had a 250 year orbit; a Pass being fifty of those years and an Interval two hundred, it was revealed by AIVAS that the orbit had changed repeatedly over the years; three times being two hundred and fifty-eight years long, and once two hundred and forty. Another problem was that both Long Intervals were mistakenly believed to be four hundred years long, when in reality they were some four hundred and fifty years long. As a result of this, the Ninth Pass was listed as having begun on 2508 AL, when in reality it had begun in 2521 AL. The dates were soon remedied, and the new system dubbed the "AIVAS Adjusted Turn".

Oddly, despite materials (such as the Dragonlover's Guide to Pern) stating Long Intervals were four hundred and fifty years in length, characters still referred to the Second Long Interval as being four hundred years in length as late as All the Weyrs of Pern. While this is of course the result of a retcon, it could also be explained along with the ot

Original Pass/Interval Dates

This timeline gives the dates as they were reco.

Alternate Calendar

In some versions of Moreta: Dragonlady of Pern, an alternate timeline, listing only the dates that each Pass began, is included in the appendices at the back of the book. Oddly, the dates given result in the Intervals all being different lengths.

In addition to this, 1505AL is given as the date of the Plague and Moreta's Ride, despite this contradicting the novels themselves, which list 1541AL - seven years before the end of the Pass - as the date of the Plague.

Since it contradicts the dates given in all the books that were published prior to it, it is not clear if it was ever considered canon, or whether it was an early draft that did not get updated.

AIVAS Adjusted Time (AAT)

At this point in time, very little is known about the AAT system. This is largely due to the fact that only a few eras of time in Pernese history have been explored, meaning the exact length of each Pass and Interval is not known.

Research from AIVAS yielded the following information;

As such, the only known dates are 8AAT to 58AAT for the First Pass and 2521 to 2568 for the Ninth Pass.

  • The First Interval is known to have been two hundred years long - not only because this date was confirmed in Dragonseye/Red Star Rising, arguably before the AL system became flawed, but also because the length of future Intervals may have been calculated using the length of the First Interval.
  • The Third Pass is recorded as having begun on 508AL - which would mean the Second Interval was two hundred and four years long - and the Sixth Pass is also known to have lasted fifty years, as confirmed by Lady Holder Nerilka of Ruatha Hold. However, these dates could be flawed for the reasons mentioned above regarding Pass and Interval Length - where the date was calculated using the incorrect belief that a Pass and Interval numbered two hundred and fifty years in length.
  • It can be assumed that the Eighth Pass would have been close to fifty years in length, as the Oldtimers would surely have noticed any changes and informed the riders of the Ninth Pass. Of course, the Oldtimers could easily have lost track time over the years and simply assumed that fifty years had passed.
Community content is available under CC-BY-SA unless otherwise noted.