Distance in the Array is based on standards inherited through the artifact tablets. They use meters, astronomical units, light years, parsecs, etc…
Time is also based on the artifact tablets, using standardized seconds, minutes and hours. Days are not as well-defined, but the week is standard (168 hours), and so the week is the usual date. 52 weeks make up a standard year.
No one in the Array knows what these measurements were originally based on.
Interstellar scale differs from Charted Space, due to the 3D element. Each sector is an 8 parsec cube, 16 x 16 x 16 spaces. Each space on a sector map is half a parsec across. Because of the number of spaces in a sector (over 4000), there are no subsectors.