▁a ▁calendar ▁era ▁( year ▁number ing ) ▁with ▁an ▁epo ch ▁( start ▁date ) ▁corresponding ▁to ▁ 2 2 M arch ▁ 1 0 6 AD . ▁It ▁was ▁the ▁official ▁era ▁of ▁the ▁Roman ▁province ▁of ▁Arab ia ▁Pet ra ea , ▁introduced ▁to ▁replace ▁d ating ▁by ▁reg nal ▁years ▁after ▁the ▁Roman ▁an nex ation ▁of ▁the ▁N ab ata e an ▁Kingdom . ▁It ▁is ▁named ▁after ▁the ▁city ▁of ▁B ost ra , ▁which ▁became ▁the ▁headquarters ▁of ▁the ▁Six th ▁Leg ion ▁station ed ▁in ▁the ▁province . ▁ ▁D ates ▁and ▁names ▁The ▁start ▁date ▁of ▁the ▁B ost ran ▁era ▁was ▁once ▁a ▁matter ▁of ▁dispute , ▁in ▁part ▁because ▁the ▁Chron icon ▁Pas ch ale ▁explicitly ▁puts ▁it ▁the ▁year ▁of ▁the ▁cons uls ▁C andid us ▁and ▁Qu adr atus , ▁that ▁is , ▁ 1 0 5 . ▁Man us cript ▁discover ies ▁from ▁the ▁C ave ▁of ▁Let ters ▁put ▁the ▁issue ▁to ▁rest : ▁the ▁era ▁of ▁B ost ra ▁began ▁in ▁ 1 0 6 . ▁The ▁B ost ran ▁calendar ▁was ▁lun is olar . ▁It ▁had ▁twelve ▁months ▁of ▁ 3 0 ▁days ▁with ▁five ▁ep ag omen al ▁days ▁at ▁the ▁end ▁of ▁the ▁year . ▁The ▁month ▁names ▁came ▁from ▁the ▁ancient ▁Mac ed onian ▁calendar , ▁although ▁N ab ata e an ▁equival ents ▁were ▁also ▁used . ▁A ▁le ap ▁year ▁came ▁once ▁every ▁four ▁years ▁in ▁the ▁B ost ran