Hydrogen Time

Time is a difficult thing to standardize because the length of any significant time period (rotation cycles, orbits, etc) is different on every planet; not to mention that time is relative to the observer's frame of reference. However, in the early galactic era, scientists developed a timekeeping system that was intended to be immediately comprehensible to any sufficiently advanced civilization: the so-called "hydrogen standard." This system used as its base unit the frequency of light emitted by the lone valence electron of the hydrogen atom as it falls back to its ground state from one hyperfine level higher, referred to more concisely as a "cycle" of the atom's valence. This value, as far as all of galactic science has been able to discern, is a universal constant, and thus it makes a good basis for a logarithmic timekeeping system.

Hydrogen Time: Logarithmic Units

This conversion table has been configured to convert between Hydrogen Time Convenience (H.T.) Units and Earth Metric Time (E.M.T.) Units. E.M.T. conversion values are presented in base-ten numerics and rounded to three decimal places, as the ratio between the E.M.T. base unit (second) and the H.T. base unit (hydrogen gigacycle) is 1:1.420405752, an irrational decimal.

---

H.T. Unit	Abbrev.	Comparative Value	E.M.T. Unit
nanochron	nc	1 hydrogen valence cycle	0.704 nanosecond
microchron	mcc	1000 hydrogen valence cycles	0.704 microsecond
millichron	mlc	1e6 hydrogen valence cycles	0.704 millisecond
chron	c	1e9 hydrogen valence cycles	0.704 second
kilochron	kc	1000 c	704.024 seconds / 11.734 minutes
mirakilochron	mikc	10 kc / 10000 c	7040.242 seconds / 117.337 minutes
magnakilochron	makc	100 kc / 100000 c	19.556 hours
megachron	mgc	1000 kc	195.562 hours / 8.148 days
miramegachron	mimgc	10 mgc	1955.623 hours / 81.4842806 Earth days
magnamegachron	mamc	100 mgc	814.843 days / 2.232 years
gigachron	gc	1000 mgc	8148.428 days / 22.324 years
terachron	tc	1000 gc	22324.460 years
petachron	pc	1000 tc	22324460.400 years
mirapetachron*	mipc	10 pc	223244604 years
exachron†	xc	1000 pc	22324460400 years

*One mirapetachron is close enough to the length of the average galactic rotation that it is often used to approximate that unit.
^†An exachron is longer than the current age of the universe.
It quickly became apparent, however, that this logarithmic system could be cumbersome to use for everyday reference. Because of this, new units were created that better align with the average sophont's perception of time. These "convenience units" quickly became the new colloquial "standard time."

Hydrogen Time: Convenience Units

This conversion table has been configured to convert between Hydrogen Time Convenience (H.T.) Units and Earth Metric Time (E.M.T.) Units. E.M.T. conversion values are presented in base-ten numerics and rounded to three decimal places, as the ratio between the E.M.T. base unit (second) and the H.T. base unit (hydrogen gigacycle) is 1:1.420405752, an irrational decimal.

---

H.T. Unit	Abbrev.	Comparative Value	E.M.T. Unit
chron	c	1/100 ty	0.704 seconds
tychon	ty	100 c	70.402 seconds
arc	arc	50 ty	58.669 minutes
hemicirc	hcrc	10 arc	9.778 hours
circ	crc	2 hcrc / 20 arc	19.556 hours
decacirc	dcrc	10 crc	8.148 days
hemimora	hmra	5 dcrc / 50 crc	40.742 days
mora	mra	10 dcrc / 100 crc	81.484 days
annua	ann	5 mra / 500 crc	407.421 days / 1.1162 years
decana	dann	10 ann	11.162 years
centana	cann	100 ann	111.622 years
kilana	kann	1000 ann	1116.223 years
epoch	epc	1000000 ann	1116223 years
eon	eon	1000000000 ann	1116223000 years

Time and Date Format

Dates are written as a succession of increasingly general timeslices, like so:

crc/dcrc/mra/ann
5/8/3/45875 AGU

Times of day are written in an opposite manner, with progressively more specific timeslices:

arc:ty:c
15:36:82

Calendar

The calendar of a standard annua is typically set up in the manner shown below: five moras, two hemimoras to a mora, five decacircs to a hemimora, ten circs to a decacirc. These units are not named; only numbered. Moras number 1-5; hemimoras number 1-10 per year or 1-2 per mora; decacircs number 1-10 per mora or 1-5 per hemimora; days number 1-10 per decacirc or 1-50 per hemimora.