fix date arithmetic to work on linux or mac
fix date arithmetic to work on linux or mac

smgoller/geode,masaki-yamakawa/geode,davebarnes97/geode,davebarnes97/geode,smgoller/geode,smgoller/geode,masaki-yamakawa/geode,davebarnes97/geode,davebarnes97/geode,jdeppe-pivotal/geode,davebarnes97/geode,davinash/geode,masaki-yamakawa/geode,jdeppe-pivotal/geode,jdeppe-pivotal/geode,masaki-yamakawa/geode,masaki-yamakawa/geode,jdeppe-pivotal/geode,masaki-yamakawa/geode,masaki-yamakawa/geode,jdeppe-pivotal/geode,smgoller/geode,jdeppe-pivotal/geode,davebarnes97/geode,davinash/geode,smgoller/geode,smgoller/geode,davinash/geode,davebarnes97/geode,jdeppe-pivotal/geode,davinash/geode,davinash/geode,smgoller/geode,davinash/geode,davinash/geode