Small documentation update of rounding issues with time arithmetic
Small documentation update of rounding issues with time arithmetic

mhvk/astropy,MSeifert04/astropy,tbabej/astropy,StuartLittlefair/astropy,stargaser/astropy,larrybradley/astropy,MSeifert04/astropy,astropy/astropy,AustereCuriosity/astropy,aleksandr-bakanov/astropy,bsipocz/astropy,larrybradley/astropy,DougBurke/astropy,lpsinger/astropy,pllim/astropy,funbaker/astropy,stargaser/astropy,bsipocz/astropy,astropy/astropy,larrybradley/astropy,pllim/astropy,StuartLittlefair/astropy,saimn/astropy,saimn/astropy,saimn/astropy,dhomeier/astropy,joergdietrich/astropy,bsipocz/astropy,funbaker/astropy,mhvk/astropy,StuartLittlefair/astropy,kelle/astropy,kelle/astropy,DougBurke/astropy,DougBurke/astropy,astropy/astropy,dhomeier/astropy,saimn/astropy,pllim/astropy,joergdietrich/astropy,mhvk/astropy,kelle/astropy,MSeifert04/astropy,saimn/astropy,AustereCuriosity/astropy,astropy/astropy,AustereCuriosity/astropy,aleksandr-bakanov/astropy,lpsinger/astropy,DougBurke/astropy,tbabej/astropy,tbabej/astropy,kelle/astropy,pllim/astropy,AustereCuriosity/astropy,aleksandr-bakanov/astropy,lpsinger/astropy,joergdietrich/astropy,AustereCuriosity/astropy,StuartLittlefair/astropy,funbaker/astropy,MSeifert04/astropy,stargaser/astropy,tbabej/astropy,lpsinger/astropy,larrybradley/astropy,joergdietrich/astropy,joergdietrich/astropy,StuartLittlefair/astropy,funbaker/astropy,dhomeier/astropy,tbabej/astropy,dhomeier/astropy,pllim/astropy,bsipocz/astropy,dhomeier/astropy,larrybradley/astropy,aleksandr-bakanov/astropy,mhvk/astropy,lpsinger/astropy,kelle/astropy,astropy/astropy,mhvk/astropy,stargaser/astropy