Visibility of Luna and Lunar Crescent

Arnhn.tic calcndar ther. are cilh.r 6 monlhs of 29 dals md 6 nonrhs of tO days. (a
notml ycar) or 5 momlB of 29 days ad 7 nonlhs of 30 da's (! lep yd).
Tnerc is no fixed nle for leap ycs in r obseNarional tunar calcndar. rhcrccdn
nol be anr. HoEver in lbe Aritineric L@d cat€tutd our ol lO yea6. cyclc t I yc6 aE
hap tcds (3Js dayt (ly.s 1994. R.igold & Dcrshowirz 20Ol_ Tsybutsty, t9Z9). l.hc
rule is rhal lhe tear nunbf /is a teap yer it
( l4 + ll.))modi0)< lt (t.4A)
Olhwisc the year is nor a teap year. In such an a.ihmelic lunar catcndor alt rhe odd
.umbeEd mon$s conlain 30 days and lhe.vd nhb.ed nonibs conhin 29 days cach.
h re lcip yedr a day is added ro $e Meltih month. in gmeFl. a srrictl, tune oalendar
ldvanc$ by I I days againj lhe solar cat.ndd. Th€refoF rhe $asons aod a orhcr
pncnom€na rhzr dcpcnd on Ihe eld cycle {to ml follow a slmcfiy lu,ar catddsr Ttc
monlb numbq 9 (R nad&) in lhe Isl6mic qtods my f.ll in wi.l{. slmmd. aurmn
Thc Luni-Solar @tfldaB d b.sielly lufu bul ro kep r&k of$e *a.ons in
prrce of adding sin8le days in a lqp ye& a whol€ monfi k addcd (inrqcshlion) lo
followthe $ld! cyclc, The Hebrew dd the Hindn qlendaG fa into thG ctass(Rcideol.t
& De6howir2 2001 . Bushwic[ 1989, ScEIt & Ditshir 1896. at_Bituni r 000. at_Btuni
l0l0).In ce ofHindu calcnds (th.y have bo$ $e $lar tud rhe luni-sotar calcndaB) a
lunarmonrh is imclcalatcdiwhcneve,irnrsinroEconpr€resotarmoilh.tncascotrhc
HcbFw l!ni,$lr cole.dar d addniomt honrh of l0 da)6 rs mrcEararcd betorc rhc
usurl 12" nonlh oflbe yce. The En ofihe dd.its of th6c calodd i, morc of$c
soc'al ahd reliSious nlrurc aod is nor in tine with tbeprcsnt*o,k.
Calend.ical cab'narioB for cacn calhdlr ha€ 6eir oM $phkhadons_ bul
bcins phcnoncnoloSicat rtE obsctualionat lunr calend., is mosr chaltensins. A tunnr
month bas lo beein wib the actuat sighling of lbe new luns cresce d.d tne conditions
I6