▁ 1 2 th ▁of ▁the ▁full ▁circle , ▁but ▁the ▁time ▁spent ▁by ▁the ▁Sun ▁in ▁each ▁sign ▁var ies ▁slightly ▁due ▁to ▁the ▁ecc ent ric ity ▁of ▁the ▁Earth ' s ▁orbit ▁ ▁The ▁path ▁of ▁the ▁Sun ▁passes ▁through ▁ 1 3 ▁const ell ations ▁recognized ▁by ▁ancient ▁Bab yl onian , ▁Greek , ▁and ▁Roman ▁astronom ers ▁( including ▁in ▁P to le my ' s ▁Al mag est ) ▁and ▁the ▁modern ▁International ▁Astronom ical ▁Union . ▁ ▁Because ▁the ▁Bab yl oni ans ▁had ▁a ▁ 1 2 - month ▁lun ar ▁calendar , ▁they ▁chose ▁and ▁divided ▁up ▁the ▁year ▁even ly . ▁ ▁The ▁ 1 3 th ▁was ▁left ▁out : ▁O phi uch us , ▁the ▁bottom ▁part ▁of ▁which ▁inter ject s ▁between ▁Sc or pio ▁and ▁S ag itt arius . ▁ ▁Occ asion ally ▁this ▁difference ▁between ▁the ▁astronom ical ▁const ell ations ▁and ▁the ▁ast ro log ical ▁signs ▁is ▁mistaken ly ▁reported ▁in ▁the ▁popular ▁press ▁as ▁a ▁" change " ▁to ▁the ▁list ▁of ▁traditional ▁signs ▁by ▁some ▁astronom ical ▁body ▁like ▁the ▁I AU , ▁NASA , ▁or ▁the ▁Royal ▁Astronom ical ▁Society . ▁This ▁happened ▁in ▁a ▁ 1 9 9 5 ▁report ▁of ▁the ▁BBC ▁N ine ▁O ' C lock ▁News ▁and ▁various ▁reports ▁in ▁ 2 0 1 1 ▁and ▁ 2 0 1 6 . ▁Professional ▁astronom ers ▁generally ▁consider ▁ast ro log y ▁a ▁pseud os cience ▁which ▁has