<P> The Jewish day is of no fixed length . The Jewish day is modeled on the reference to "...there was evening and there was morning ..." in the creation account in the first chapter of Genesis . Based on the classic rabbinic interpretation of this text, a day in the rabbinic Hebrew calendar runs from sunset (start of "the evening") to the next sunset . In most populated parts of the world this is always approximately 24 standard hours, but, depending on the season of the year, it can be slightly less or slightly more . Halachically, a day ends and a new one starts when three stars are visible in the sky . The time between true sunset and the time when the three stars are visible (known as' tzait ha'kochavim') is known as' bein hashmashot', and there are differences of opinion as to which day it falls into for some uses . This may be relevant, for example, in determining the date of birth of a child born during that gap . </P> <P> There is no clock in the Jewish scheme, so that the local civil clock is used . Though the civil clock, including the one in use in Israel, incorporates local adoptions of various conventions such as time zones, standard times and daylight saving, these have no place in the Jewish scheme . The civil clock is used only as a reference point--in expressions such as: "Shabbat starts at ...". The steady progression of sunset around the world and seasonal changes results in gradual civil time changes from one day to the next based on observable astronomical phenomena (the sunset) and not on man - made laws and conventions . </P> <P> In Judaism, an hour is defined as 1 / 12 of the time from sunrise to sunset, so, during the winter, an hour can be much less than 60 minutes, and during the summer, it can be much more than 60 minutes . This proportional hour is known as a sha'ah z'manit (lit . a timely hour). A Jewish hour is divided into 1080 halakim (singular: helek) or parts . A part is 31⁄3 seconds or / minute . The ultimate ancestor of the helek was a small Babylonian time period called a barleycorn, itself equal to / of a Babylonian time degree (1 ° of celestial rotation). These measures are not generally used for everyday purposes . </P> <P> Instead of the international date line convention, there are varying opinions as to where the day changes . One opinion uses the antimeridian of Jerusalem . (Jerusalem is 35 ° 13' east of the prime meridian, so the antimeridian is at 144 ° 47' W, passing through eastern Alaska .) Other opinions exist as well . (See International date line in Judaism .) </P>

What type of calendar was used in biblical times