Added time

cons-space.md

@@ -109,6 +109,10 @@ Note that in this definition a string is not an atom, which is probably right. B
 
 Note, however, that there's a risk that we might have two instances of strings comprising identical characters in identical order, one of which was bound in a namespace and one of which wasn't; string equality is something to worry about.
 
+### TIME
+
+At nanosecond resolution (if I've done my arithmetic right), 128 bits will represent a span of 1 x 10²² years, or much longer than from the big bang to the [estimated date of fuel exhaustion of all stars](https://en.wikipedia.org/wiki/Timeline_of_the_far_future). So I think I'll arbitrarily set an epoch 14Bn years before the UNIX epoch and go with that. The time will be unsigned - there is no time before the big bang.
+
 ### TRUE
 
 The canonical true value. May not actually exist at all: the cell-pointer whose value is one is deemed to point to the canonical true value. However, if one is a valid cell-pointer, the cell at pointer zero will be initialised with the tag "TRUE" (i.e. the 32 bit unsigned integer which, when considered as an ASCII string, reads "TRUE"). The count of the TRUE cell is the maximum reference count value - that is, it can never be garbage collected. The mark is always 1 - that is, it can never be garbage collected. The access control value is TRUE: any user can read the canonical true value. The payload is zero.