If the new moon was seen a day earlier in another part of the country, which does sometimes happen, then the brethren in that area would be in disobedience by not keeping the Appointed Times as they should. Yahshua’s statement in the New Testament addressing the idea of worship not being in Jerusalem alone is revealing:
  Yahshua saith unto her, Woman, believe me, the hour cometh, when ye shall neither in this mountain, nor yet at Jerusalem, worship the Father. Ye worship ye know not what: we know what we worship: for salvation is of the Jews. But the hour cometh, and now is, when the true worshippers shall worship the Father in spirit and in truth: for the Father seeketh such to worship him. Elohim is a Spirit: and they that worship him must worship him in spirit and in truth, John 4:21-24.
  The temple was destroyed in 70 A.D. and worship now is where two or more meet together: For where two or three are gathered together in my name, there am I in the midst of them, Matt 18:20.
  His people have His Spirit within them, 1 Cor 3:16; 6:19; 2 Cor 6:16. Since we are spread out across the world, we do our best to come together in obedience to His commands to meet and worship together:
  And Yahweh spake unto Moses, saying, Speak unto the children of Israel, and say unto them, Concerning the feasts of Yahweh, which ye shall proclaim to be holy convocations, even these are my feasts. Six days shall work be done: but the seventh day is the sabbath of rest, an holy convocation; ye shall do no work therein: it is the sabbath of Yahweh in all your dwellings. These are the feasts of Yahweh, even holy convocations, which ye shall proclaim in their seasons, Lev 23:1-4.
  The command of keeping a “holy convocation” literally means that we are to be meeting together to keep any of Yahweh’s commanded moeds (Appointed Times). In the future Kingdom it will be in Jerusalem (Isa 66:23; Zech 14:16), but for now we do the best we can with Yahweh and Yahshua’s help, in Spirit and in Truth.

  We actually do in preparation for the next year’s Feast days, but we still practice the ancient ways of looking for the new moon. They didn’t have the technology we have today. And we may not either, in the near future.
  One may know when the time is estimated for the setting of the sun on a Sabbath, but mechanical watches can break. We should wait until we actually see the sun setting down below the horizon before declaring a new moon day. We could lose Internet and phone services due to tribulation or other reasons. Even so, we will still need to keep Yahweh’s Appointed Times. We all need to be practicing these things in obedience. It may be a big test for many, one that prayerfully we’ll all pass. We are to observe those “lights” that Yahweh put in heaven for a reason, Gen 1:14-19.

  The Ryrie Study Bible’s note points out the 81st Psalm is associated with the Feast of Tabernacles. That is a special time on Yahweh’s calendar. Four of the seven “moedim” Feast days occur in this month. It is a glorious time of deep repentance followed by the good news of the first resurrection and then the promise of the coming Kingdom. This new moon (also translated month) is the “fullest” of monthly blessings for the faithful.
  Instructions given for observing Tabernacles and Atonement are based on observance of the new crescent moon. So why mention the “full moon”? Most likely this is a poetic or exuberant expression of expectations of the final feast of the year. It is “full” of good news.

  At certain times of the year it would be impossible to see the new moon from that far north. Alaska will have constant sunlight, in parts of the year, as the sun seems to float along the horizon around in a flat clockwise movement. In such situations it is has been agreed that it would be best to default to another area (further south) where brethren could confirm the new moon. The idea that Yahweh desires mercy and not sacrifice comes to mind.
  It has been the common understanding and agreement among most of the major Sacred Name Assemblies in the United States, for example, to allow two or three reliable witnesses (Deut 19:15; 2 Cor 13:1) to confirm a new moon sighting wherever they may be within the nation, even though they may be in different time zones. The United States has four time zones, while other countries may have only one. It seemed appropriate to make all of North America inclusive for the reasons stated. Those from different areas or time zones will travel to the sojourning Feasts such as the Feast of Tabernacles in obedience to Yahweh. Besides the North America region, there would be the regions of South America, Europe, Asia, Africa, Australia, and the Middle East .

  Sometimes it’s best to answer a question with a question. If one was to travel to a different country would they keep the 7th day Sabbath according to their own region or the region that they come into? The answer would obviously be the region that they came into, and it would be the answer to any other Appointed Times. The weekly Sabbath is from Friday night sunset to Saturday night sunset wherever you may be.

  Regrettably the world and it’s way of doing things is not in-line with Yahweh’s ways. We are told to come out of symbolic Babylon and it’s false worship. In thinking how Yahweh wants us to keep His Feast days, let’s consider the 4th day of creation:
   And Elohim said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years, Gen 1:14.
The word for “seasons” is Strong’s #4150 {moed} meaning, “appointed times.”   In other words, these lights, such as a visible new moon are part of Yahweh’s calendar for setting Appointed Times (Feast days). His calendar is both lunar and agriculturally based.   Notice the following scriptures for the agriculture connection in Yahweh’s calendar:
• Lev 23:10-11 Wavesheaf (first fruit offering) of barley offered during early Spring. This is done in the first month of Yahweh’s calendar, verses 4-5.
• Ex 9:31 7th plague of hail destroys Abib of barley, just before Passover occurred. Israel is looked upon for confirmation for the early barley grain, since Isreal has been designated as the “holy land” by Yahweh, Zech 2:12.
• Lev 2:14 Abib (early grain)
• Deut 16:1; Ex 34:18 First month of the year is called, “the month of Abib.” It’s in the Spring, not in the dead of winter.