docs(datetime): update datetime API docs
docs(datetime): update datetime API docs

references #5010

alan-agius4/ionic,TillaTheHun0/ionic,driftyco/ionic,jarrodkoch/ionic,jhlee8804/ionic,cambronjay/ionic,jhlee8804/ionic,janglednerves/ionic,jhlee8804/ionic,driftyco/ionic,jarrodkoch/ionic,jarrodkoch/ionic,TillaTheHun0/ionic,dennybiasiolli/ionic,dennybiasiolli/ionic,driftyco/ionic,joshesp/ionic,joshesp/ionic,manucorporat/ionic,janglednerves/ionic,janglednerves/ionic,AbraaoAlves/ionic,alan-agius4/ionic,cambronjay/ionic,manucorporat/ionic,jhlee8804/ionic,manucorporat/ionic,driftyco/ionic,cambronjay/ionic,alan-agius4/ionic,alan-agius4/ionic,alan-agius4/ionic,AbraaoAlves/ionic,jhlee8804/ionic,TillaTheHun0/ionic,AbraaoAlves/ionic,jarrodkoch/ionic,dennybiasiolli/ionic,dennybiasiolli/ionic,TillaTheHun0/ionic,AbraaoAlves/ionic,janglednerves/ionic,manucorporat/ionic,joshesp/ionic,jarrodkoch/ionic,manucorporat/ionic,joshesp/ionic,cambronjay/ionic,AbraaoAlves/ionic,cambronjay/ionic,dennybiasiolli/ionic,janglednerves/ionic,driftyco/ionic,brianespinosa/ionic2-sass,alan-agius4/ionic