+ (dating system)

A dating system was in use on Kandoka's moon that featured a "+" symbol preceding a number.

A year had at least thirteen months. The eleventh month contained at least twenty-eight days, the twelfth at least nine, and the thirteenth at least thirty-five.

The Thirteenth Doctor and her companions visited Kerb!am in the year +135 after receiving a request for help. (TV: Kerblam!)