ila , ▁The ▁E agle , ▁was ▁possibly ▁associated ▁with ▁the ▁z od iac ▁by ▁virtue ▁of ▁its ▁main ▁star , ▁Al ta ir . ▁H yd ra ▁in ▁the ▁Early ▁Bron ze ▁Age ▁marked ▁the ▁cel est ial ▁equ ator ▁and ▁was ▁associated ▁with ▁Leo , ▁which ▁is ▁shown ▁standing ▁on ▁the ▁ser pent ▁on ▁the ▁D end era ▁z od iac . ▁Cor v us ▁is ▁the ▁Crow ▁or ▁R aven ▁myster iously ▁per ched ▁on ▁the ▁tail ▁of ▁H yd ra . ▁ ▁Table ▁of ▁dates ▁▁ ▁The ▁following ▁table ▁comp ares ▁the ▁Greg or ian ▁dates ▁on ▁which ▁the ▁Sun ▁enters : ▁a ▁sign ▁in ▁the ▁P to le ma ic ▁tropical ▁z od iac ▁a ▁sign ▁in ▁the ▁H indu ▁sid ere al ▁system ▁( date ▁given ▁below ▁may ▁change ▁by ▁one ▁or ▁two ▁days ▁each ▁year ) ▁the ▁astronom ical ▁const ell ation ▁of ▁the ▁same ▁name ▁as ▁the ▁sign , ▁with ▁const ell ation ▁boundaries ▁as ▁defined ▁in ▁ 1 9 3 0 ▁by ▁the ▁International ▁Astronom ical ▁Union . ▁ ▁The ▁theoretical ▁beginning ▁of ▁A ries ▁is ▁the ▁moment ▁of ▁v ernal ▁equ ino x , ▁and ▁all ▁other ▁dates ▁shift ▁accordingly . ▁ ▁The ▁precise ▁Greg or ian ▁times ▁and ▁dates ▁vary ▁slightly ▁from ▁year ▁to ▁year ▁as ▁the ▁Greg or ian ▁calendar ▁sh ifts ▁relative ▁to ▁the ▁tropical ▁year . ▁These ▁variations ▁remain ▁within ▁less ▁than ▁two ▁days ' ▁difference ▁in ▁the ▁recent ▁past ▁and ▁the ▁near - f uture , ▁v ernal