plt/racket — pull request #726 by Kalimehtar (2014-07-11 10:45:32+00:00)
Title: Fix _date to allow dates before 1970 year

In current version one cannot get date before 1970, because seconds->date doesn't allow such dates.
But `date' struct doesn't have such restriction, so it is better to drop day-of-year (one can calculate it if needed), than disallow all dates before 1970