D'ni time operates on a much different system than surface time does. Each system has a year of the same length, but the months, days, hours, and even the seconds are of different lengths in D'ni. There is also apparently no deliniation of a week's time. Timekeeping goes straight from days to months.
The most complete description of the system is found in a flyer in the classrooms of neighborhoods with clocks. This flyer was released by the DRC in March, 2007. The following is from the classroom brochure.
The hahr (har) is the largest known quantity of time on the D'ni calendar. It is roughly equivalent to one year in the Gregorian calendar.
A vailee (vIlE) is roughly equivalent to a month. There are 10 equal vaileetee in each hahr. Their approximate respective dates on the Gregorian calendar are:
- Leefo: April 21 - May 27
- Leebro: May 28 - July 3
- Leesahn: July 3 - August 8
- Leetar: August 9 - September 14
- Leevot: September 14 - October 20
- Leevofo: October 21 - November 26
- Leevobro: November 26 - January 1
- Leevosahn: January 2 - Febuary 7
- Leevotar: Febuary 7 - March 15
- Leenovoo: March 16 - April 21
Due to fluctuations in the length of a Gregorian calendar's year versus a D'ni hahr, these dates shift back and forth by as much as a couple of days in either direction from year to year.
A yahr ( yar) is the length of a day in the D'ni timekeeping system. Each yahr is equal to about 30 hours and 14 minutes (1.26 Earth solar days). There are 29 yahrtee in each vailee, and 290 yahrtee in one hahr.
Every yahr is divided into five equal segments called gahrtahvotee. Each gahrtahvo (gartavo) is equal to about 6 hours and 3 minutes. Aitrus's watch illustrates gahrtahvotee as segments with varying degrees of brightness.
The pahrtahvo (partavo) is the D'ni equivalent of the hour measurement in solar time — 1 hour 13 minutes, to be more precise. Each yahr contains 25 pahrtahvotee; accordingly, each gahrtahvo contains five pahrtahvotee. This is also the unit of time that is referred to as "nth bell" in the Book of Ti'ana. The clocks found in many D'ni neighborhoods also use this division of time. Older official descriptions of the D'ni system did not mention this unit, and merely described the gahrtahvotee as being divided into 25 tahvotee. Most, if not all, explorer-written D'ni clock programs still rely on this older description.
A tahvo (tavo) is roughly 14.5 minutes of solar time. There are five tahvotee in each pahrtahvo.
A gorahn (goran) is equal to about 35 seconds of solar time. There are 25 gorahntee in each tahvo.
The prorahn is the smallest known unit of time in D'ni timekeeping. Each prorahn is about 1.5 solar seconds long, and there are 25 of them in each gorahn.
BE and DE
Coined by the D'ni Restoration Council, the terms BE (Before Earth) and DE (D'ni Era) are used to distinguish periods of the D'ni civilization timeline before their arrival on Earth and afterwards. These terms also help in the conversion of D'ni hahrtee to surface/Earth years. Similar to Earth's own BC and AD, the DRC count backward when using BE (1 BE would be 1 year before the Ronay left Garternay for Earth), and forward when using DE (1 DE being 1 year since D'ni was established).
Converting to and from the Gregorian calendar and solar time
The conversions in the classroom brochure and the dates corresponding to the vaileetee are approximations, since the D'ni year does differ slightly from the length of an Earth year in the Gregorian calendar. For example, the actual date of Leefo 1, the D'ni New Year, will vary slightly from year to year, sometimes falling on April 20 and sometimes on April 21.
During the course of Mysterium 2006, RAWA revealed that the length of the D'ni year is equivalent to the precise number of seconds in the Mean Solar Tropical Year in 1995. In October 2007, he revealed in correspondence to explorer RIUM+ that the exact value is 31556925.216 seconds, or 365.24219 days. RAWA also disclosed the day and time at which the D'ni and Gregorian calendars converged exactly: April 21, 1991 at 9:54 AM Pacific Daylight Time (UTC-0700), which is the date/time stamp on the original HyperCard Stack file for Myst.
The following tools can be used to automatically convert dates and times between the D'ni and Gregorian calendars:
Journal Dating System
The journals that appear in Riven, Exile, and Revelation are dated using an odd sort of shorthand that doesn't seem to match up to the actual surface dates of the events. However, this is due to the way in which D'ni dates (written in base 25) were converted to our numeric system of base 10.
These dates are given in year.month.day form. For example, Gehn's journal in Riven states that Catherine arrived on "86.9.29", which is Leevotar 29, 9461 (surface date March 15, 1806). The year part of the date is in a shorthand form, much as we might write "04" instead of "2004", leaving off the century part of the year. The shorthand is based on the D'ni century (hahrtee fahrah), which is 625 years long, or 100 years in base-25 notation. The current D'ni century began in 9375 DE (%00 in base 25), or 1719 CE. The hahr 9461 DE is %3! in base 25. Dropping the century leaves 3!, or 86 in base 10.
For more information on converting between base 25 and base 10, please consult the article on D'ni numerals.
There are several known examples of D'ni clocks, watches, and timers:
- This would be the first hahr of the 16th hahrtee fahrah, since the D'ni system began in 0 DE, unlike our Gregorian CE/BCE system, which has no year 0.