Sanhedrin, Chapter Five, Mishnah Three
Mishnah three deals with invalidating the testimony due to discrepancies between the testimony of the two witnesses.
1) If one said, On the second of the month, and the other said, On the third, their evidence remains valid, since one may have known that the month was intercalated and the other may not have known that the month was intercalated.
a) If one said, On the third and the other said, On the fifth, their evidence is invalid.
2) If one said, At the second hour, and the other said, At the third, their evidence remains valid.
a) If one said, At the third hour, and the other said, At the fifth, their evidence becomes invalid.
b) Rabbi Judah says: It remains valid. [But] if one said, At the fifth hour and one said At the seventh, their evidence becomes invalid, since at the fifth hour the sun is in the east and at the seventh it is in the west.
This mishnah deals with discrepancies between the testimony of the witnesses with regards to the time at which the crime was committed.
Section one: If there is a discrepancy of one day between the witnesss testimony it is not invalidated. This is due to the intercalation of the Jewish month. Jewish months go according to the cycles of the moon. There are between 29 and 30 days in a lunar month. Therefore some months are of 29 days and some are of 30. In the time of the Mishnah the Jewish calendar was not yet fixed. This meant that at the end of every month, on what was potentially the 30th day of the month, the court would need to decide if the current day was the first of the next month or the last of the previous month. According to our mishnah, witnesses may not know that the previous month was actually a 30 day month and therefore they may not know the exact current date. Hence, a one day discrepancy does not invalidate their testimony. A two day discrepancy does, however, invalidate their entire testimony.
Section two: At the time of the Mishnah daytime was divided into 12 hours, no matter how long the actual day. During the summer the hours would be longer and during the winter they would be shorter. A one hour discrepancy between the two witnesses is not significant and therefore does not invalidate their testimony. This makes strong sense if we remember that they certainly did not have clocks in the time of the Mishnah. A two hour discrepancy does invalidate the testimony. It is assumed that although they did not have clocks, people were able to chart the sun and thereby keep rough track of time. Rabbi Judah disagrees. According to him sometimes even a two hour discrepancy between the witnesses does not invalidate the testimony. If the discrepancy was all within one period of the day, it does not invalidate the testimony. If, however, it was between the fifth and seventh hour, in other words between the first half and the second half of the day, at the time when the sun would pass from the east to the west, the testimony would be invalidated, since this is a point of time that most people would recognize.