1,268. One Day or Two?

Hilchos Kiddush HaChodesh 5:9

Whether holidays are observed for one day or for two days is not solely dependent on a land’s geographic distance. If a place is a journey of five days or less from Jerusalem so that the messengers could certainly reach them, we do not assume that the residents observe only one day of yom tov because we have no way of knowing whether or not the messengers actually went there. Maybe they didn’t travel to this particular place because there were no Jews living there at that time. If such a location became populated by Jews only after we started establishing dates based on the fixed calendar, the residents would have to observe two days of yom tov. Other reasons that the messengers might not travel to a certain location include the presence of an impeding blockade, which was the case between Jerusalem and the Galilee in the time of the Mishna, and Samaritans preventing the messengers from passing through.

Hilchos Kiddush HaChodesh 5:10

If the number of days observed depended exclusively on a location’s geographic distance, then the residents of Egypt would observe yom tov for just one day because the messengers of Tishrei could have reached them. A journey from Jerusalem to Egypt by way of Ashkelon would take eight days or less. The same is true for most of Syria. We see from this that the matter is not solely contingent upon a land’s geographic distance.