A Clear Day

Could you please clarify the Orthodox view of when a "day" ends and the next day begins. I always understood that a day ends at sundown and the next day begins immediately after sundown. I heard that another opinion states that, in Judaism, each day is counted from "dawn to dawn". Thank you.

The Jewish day has always begun at night and continues on to the next night. The Oral Torah in the Babylonian Talmud at the very beginning, Tractate Berachot, learns from the syntax of the verse that describes the very first day of the creation that the Jewish day begins with the night. The verse states, Genesis 1:5, "And God called the light day and the darkness He called night, and it was night and it was day - the first day".