Back when the months of the Jewish calendar were determined by observations of the new crescent moon, eyewitnesses would bring their testimony to the rabbinical court in Jerusalem, and the court would sanctify the new month based on this testimony. Since a lunar month is about 29 ½ days, a Hebrew month (which has to have a whole number of days) can have either 29 or 30 days. So the court then had to get the word out to the rest of the Jewish world about which day had been declared the first of the month, so that everyone could observe the holidays on the same day. Originally this was done by signal fires (as in The Lord of the Rings), which transmitted the message rapidly. But then the Cutheans, a sect opposed to the rabbis, launched the first phishing scam and made signal fires on the wrong days to throw people off.
When did the "phishing scam" occur?