YES, you read the title "Why Seventh-day Adventists Keep Sunday in Tonga" correctly. Adventists in Tonga keep the same day as the Methodists, Roman Catholics, and Mormons; and here is the reason.
Tonga, or the Friendly Islands, lies in the South Pacific Ocean, nearly due south of Samoa and southeast of Fiji. The international date line, which begins the day, runs between Samoa and Fiji. It follows roughly the meridian 180 degrees. However, for commercial reasons, the Tongan Government had the date line placed east of Tonga so they would have the same day as New Zealand and Fiji. Tongan commerce is mainly with New Zealand and Fiji. The Tongan people are the same as the Samoans, and they are on the same longitude line; and thus have the same time but, strange to say, keep different days.
The need for a date line is apparent. As people traveled from the old world both east and west they discovered upon meeting on the other side of the world that they were keeping different days. As the day must begin somewhere, by common consent the meridian 180 degrees was decided upon. Here a line could be drawn from the North Pole to the South without running through any great land mass. This was the only suitable and no doubt providential place in the world for the date line. This is where the new day begins.
The Encyclopaedia Brittanica clearly states that mariners have generally adopted the 180th meridian, situated in the Pacific Ocean, as a convenient line for coordinating dates. The so-called International Date Line, which is, however, practically due to American initiative, is designed to remove certain objections to the meridian 180 W, the most important of which is that a group of islands lying about this meridian differ in date by a day, although only a few miles apart. Several forms have been suggested; these generally agree in retaining the meridian 180 in the mid-Pacific, with a bend in the north in order to make the Aleutian Islands and Alaska of the same time as America, and also in the south so as to bring certain of the South Sea Islands into line with Australia and New Zealand.
Tonga is in a unique position. A. H. Wood says:
Tonga is actually in the Western Hemisphere, but in spite of this it observes eastern time, that is, the same time as places in the Eastern Hemisphere (Europe, Asia, etc., and as far as Fiji) and not the time of the Western Hemisphere (America, etc). For instance, when it is 2:20 P.M. Thursday in Nukualofa (Tonga) it is 2:00 P.M. at Suva (Fiji), 1:30 P.M. in Auckland (New Zealand), 12 noon at Sydney, and 2:00 A.M. at London—all these places being on Thursday—but it is Wednesday 6:00 P.M. at San Francisco (USA) and 2:30 P.M. in Tonga; nevertheless, the day is rightly called Wednesday in Samoa, while in Tonga it is called Thursday, owing to the fact that, as Tonga's commercial dealings are chiefly with Australia, New Zealand and Fiji, it observes the same day as those countries.— History and Geography of Tonga (1932), p. 70.
Thus in Tonga the days of the week were wrongly named, as Pastor Butz, a pioneer missionary to Tonga, wrote in a Tongan tract in 1895:
The first missionaries who came to Tonga, Samoa, Nuie, Rarotonga and Tahiti, came from the west to the east; but they did not know that they had crossed the line where the day begins and ends. So they did not drop a day as they should have done, and they taught the people of these islands the names of the days wrongly; therefore the first day of the week was called the second day of the week, and the second the third, the third the fourth, the fourth the fifth, the fifth the sixth, the sixth the seventh, and the seventh day the first day of the week.
When the Europeans who followed the missionaries came to these islands, they found the days wrongly named and they corrected the names of the days in Tahiti, and then did so in Samoa. But in Rarotonga, Nuie and Tonga, they observed the wrong time till the beginning of the year 1900, and then corrected the error in Rarontonga and Nuie so in Tonga only the days are still wrongly named. —Tongan Tract on Dateline, by Pastor Butz, 1895.
Sir Thomas Henley, who traveled extensively throughout the South Pacific, wrote:
Tonga starts the world's prayers. Actually it is on the eastern side of the International date-line and should observe American time, as does Samoa; but as its commercial relations are almost entirely with Fiji, New Zealand and Australia it observes the time kept by countries on the western side of the line. —A Pacific Cruise, p. 45.
He further states:
The date-line actually passes through the eastern portion of the Fiji group, but naturally no change is observed within the group. The Tongan Group, or Friendly Islands, are about 300 miles east of the so-called date-line. When the early missionaries arrived there over 100 years ago from Australia, forgetful or unaware of the effect of the 180th meridian on time, they established the practice of recognizing days of the week, as observed in Australia and New Zealand, lying far to the west of the meridian. Therefore the establishment of Sunday observance in Tonga upon the same day as observed in Australia was incorrect, as strictly speaking, the day is Saturday, west longitude.
When the Seventh-day Adventists subsequently went to Tonga from America they did not need to change the day, and so continued the observance of the day already observed, which is really Saturday, the seventh day of the week.—Ibid., p.
It should be noted that these authorities admit that in Tonga the day called Sunday is really the seventh day of the week and hence the Sabbath of the Lord. The government officials of Tonga also agree that Sunday there is the seventh day. It should be always remembered that the curve that was made in the date line to bring Tonga into the same days as New Zealand and Fiji was done for commercial reasons. There was no thought or suggestion of anything religious in this act. It was for commercial reasons only.
It is also interesting to note that the Encyclopaedia Brittanica refers to the date line as "the so-called International date-line," for it is in a sense not "international" at all. Any country has a right to call its days any names it chooses. Thus the Tongan Government had a full right to place the date line either east or west of their territory. For commercial advantages they choose to place it to the east of Tonga. However, when it comes to the question of obeying God and keeping the "Sabbath of the Lord thy God," this must not be decided by any earthly power or government. If a government decided to change the name of the days of the week to aid their commerce, this must not interfere with our obedience to God and the keeping of the Lord's day. If an earthly government calls the seventh day of the week Sunday, it does not therefore make it the first day of the week. The Adventists of Tonga are determined to keep "the Lord's day"—"the Sabbath of the Lord thy God." For example, if a blank-day calendar was adopted and thus the Sabbath would fall on a different day of the week each year, we would ignore the name of the day and keep the seventh day of the week; so in Tonga our faithful people hold to God's Sabbath despite the fact that for commercial reasons it happens to be called Sunday.
Some who have never been to Tonga have maintained that our people there should keep a different day from Sunday-keepers just to be different. The big question is whether we are obedient to our Lord, and not different to others. If a blank-day calendar were adopted by the world, it would mean that one year in every seven Seventh-day Adventists would go to church on the same day as Sundaykeepers, and for that year that day would be called Sunday, whereas in actual fact it would be the seventh day—the Sabbath of the Lord.
Of course, our people in Tonga observe the Sabbath from sunset, whereas Sunday-keepers keep it from midnight to midnight. Thus when preaching God's truth we were able to show that even in Tonga the Sundaykeepers were keeping a small part of God's day. Further, it was shown to them that God's Sabbath, like all days, travels around the earth in a straight line from pole to pole. It does not move around at the angle of forty-five degrees. Thus when it is the Sabbath in Samoa it will be the Sabbath in Tonga, for Samoa is on the same line as Tonga, as stated so clearly by A. H. Wood in his history of Tonga.
The Sabbath of our Lord cannot be changed by ecclesiastic authority or earthly governments. It is the Lord's day, "the queen of days," which our Lord crowned with His own blessing. _On this clay _the manna of heaven falls. This is the day we must love and keep whether it is convenient or inconvenient, and this is what our faithful people in Tonga endeavor by God's grace to do.