Helek
The helek is a unit of time used in the calculation of the Molad. Other spellings used are chelak and chelek, both with plural chalakim.
The hour is divided into 1080 halakim. A helek is 3 seconds or 1/18 minute. The helek derives from a small Babylonian time period called a she, meaning '"barleycorn", itself equal to 1/72 of a Babylonian time degree.
The Hebrew calendar defines its mean month to be exactly equal to 29 days 12 hours and 793 halakim, which is 29 days 12 hours 44 minutes and 3 seconds. It defines its mean year as exactly 235/19 times this amount, or 365.2468222 days.
