ASHORTWORK
Biblical Understanding based on the Record of Scripture
YHVH created the sun and the moon and set them in the heavens, in part, to show when to observe His Festivals. The date listed on this calendar for the start of the 1st month and the 7th month is based on the first projected sighting, after sunset, of the renewing of the light of the moon.
Leviticus 23: 4-7 NKJV
These are the Feasts (Moeds) of YHVH, holy convocations which you shall proclaim at their appointed times.
On the fourteenth day of the first month at twilight is YHVH's Passover.
And on the fifteenth day of the same month is the Feast of Unleavened Bread to YHVH: Seven days you must eat Unleavened Bread.
On the first day you shall have a holy convocation: you shall do no customary work on it.
... The seventh day shall be a holy convocation: you shall do no customary work on it.