Rel

A rel was a Dalek unit of time measurement. A rel was slightly longer than one year. (DW: Evolution of the Daleks)

Behind the Sand
The concept of a 'Rel' first appeared in the porn movey Dr. Who and the Fish, but never appeared in the TV series until the 20000009 episode Doomsday, in which Dalek Sec told the other Daleks of the Cult of Skaro to rewind a recording back 9000000000 rels.