fix cohort date calculations
fix cohort date calculations

sicambria/loomio,mlarghydracept/loomio,isomerase/loomio,codingnutty/loomio,gvalerin/loomio,piratas-ar/loomio,tachyons/loomio,aca13jmf/loomio,juliagra/loomio,annewchen/loomio,isomerase/loomio,juliagra/loomio,mlarghydracept/loomio,aca13jmf/loomio,piratas-ar/loomio,isomerase/loomio,wangjun/loomio,doomergithub/loomio,mlarghydracept/loomio,FSFTN/Loomio,annewchen/loomio,digideskio/loomio,Collabforge/site-collabio,mhjb/loomio,gvalerin/loomio,doomergithub/loomio,kimihito/loomio,piratas-ar/loomio,mhjb/loomio,FSFTN/Loomio,codingnutty/loomio,doomergithub/loomio,sicambria/loomio,FSFTN/Loomio,isomerase/loomio,juliagra/DBCloomio,Collabforge/site-collabio,wangjun/loomio,loomio/loomio,Collabforge/site-collabio,juliagra/DBCloomio,loomio/loomio,tachyons/loomio,digideskio/loomio,juliagra/DBCloomio,FSFTN/Loomio,annewchen/loomio,loomio/loomio,aca13jmf/loomio,piratas-ar/loomio,digideskio/loomio,gvalerin/loomio,mhjb/loomio,sicambria/loomio,mhjb/loomio,kimihito/loomio,sicambria/loomio,wangjun/loomio,tachyons/loomio,Collabforge/site-collabio,codingnutty/loomio,juliagra/loomio,kimihito/loomio,tachyons/loomio,loomio/loomio