SO WHEN IS IT?

There are several different schools of thought as to when it is.
As for the time of the day, or the duration of the Sabbath there are several clues to it's occurrence.

Although many present-day church goers only observe two daylight hours of Sunday (typically 10:00am- 12:00pm) as their Sabbath one actually finds it begins at dark:

NEH 13:19 And it came to pass, that when the gates of Jerusalem began to be dark before the sabbath, I commanded that the gates should be shut, and charged that they should not be opened till after the sabbath: and some of my servants set I at the gates, that there should no burden be brought in on the sabbath day.

Note: The word dark here is tsalal in Hebrew. It is a primary word meaning to shade.

and it continues for 24 hours (not just two) as we find in:

LEV 23:32 It shall be unto you a sabbath of rest, and ye shall afflict your souls: in the ninth day of the month at even, from even unto even, shall ye celebrate your sabbath.

Note: The word even here is 'ereb in Hebrew. It means dusk and is derived from the primary word 'arab which means to grow dusky at sundown.

In the Complete Works of Josephus (who lived A.D. 37- c.100) we also find two clues about when they observed the Sabbath.

LIFE 54 reads:

"Upon his saying this, Justus came in and commended him for what he had said, and persuaded some of the people to be of his mind also. But the multitude were not pleased with what was said, and had certainly gone into a tumult, unless the sixth hour, which was now come, had dissolved the assembly, at which hour our laws require us to go to dinner on Sabbath days; so Jonathan and his colleagues put off their council till the next day, and went off without success."

and also,
The Wars of the Jews, Book 4, Chapter 9, section 12 reads:

"...where one of the priests stood of course, and gave a signal beforehand, with a trumpet, at the beginning of every seventh day, in the evening twilight, as also at the evening when the day was finished, as giving notice to the people when they were to leave off work, and when they were to go to work again."

The sixth hour may have been 6:00 pm, and the evening twilight leaves little room for debate as to when they observed their Sabbaths in the days of Josephus. Also note, if they were in fact observing the Sabbath incorrectly (during the days of Christ Jesus) you might expect to find some reference to it in the scriptures, however no such remarks occur to my knowledge.

As for what day of the week it is observed on, again there are several schools of thought, which include (at least): Friday, Saturday, Sunday, and Tuesday for 1995.

• Friday (dusk) - Saturday (dusk): Today's Jews and Seven Day Adventists both observe the sabbath during these hours.

It is important to note here how fanatical the Pharisee sect of the Jews of Yahshua's day were, as this may well be a clue to when the sabbath was observed in the region then. They were not willing to admit to any faults with the laws they observed. Note that to look at Jerusalem today is akin to looking into a time- capsule of the past. They do today, just as their fathers have always done before them. Still unwilling to be told that anything they are doing is wrong. This was evident from Yahshua's comments in:

MAT 6:1 Take heed that ye do not your alms before men, to be seen of them: otherwise ye have no reward of your Father which is in heaven.
MAT 6:2 Therefore when thou doest thine alms, do not sound a trumpet before thee, as the hypocrites do in the synagogues and in the streets, that they may have glory of men. Verily I say unto you, They have their reward.
MAT 6:3 But when thou doest alms, let not thy left hand know what thy right hand doeth:
MAT 6:4 That thine alms may be in secret: and thy Father which seeth in secret himself shall reward thee openly.
MAT 6:5 And when thou prayest, thou shalt not be as the hypocrites are: for they love to pray standing in the synagogues and in the corners of the streets, that they may be seen of men. Verily I say unto you, They have their reward.
MAT 6:6 But thou, when thou prayest, enter into thy closet, and when thou hast shut thy door, pray to thy Father which is in secret; and thy Father which seeth in secret shall reward thee openly.
MAT 6:7 But when ye pray, use not vain repetitions, as the heathen do: for they think that they shall be heard for their much speaking.
MAT 6:8 Be not ye therefore like unto them: for your Father knoweth what things ye have need of, before ye ask him.

Today, almost 2000 years later, their decedents still visit the Wailing Wall (of King Herod's Temple) in Jerusalem and use the same vain repettitions their fathers incessantly uttered. This gives one an idea as to how vigilant their traditions are. Knowing their convictions are so ingrained, the fact they persist in observing the sabbath from Friday (dusk) until Saturday (dusk) carries a reasonable amount of validity with it.

Saturday:
A minority of Roman Catholics believe the sabbath was on Saturday and the church paganized it by moving it's observance to Sunday. About 15 years ago there was such a uproar in the church several new decrees were issued. They included that: divorced people were no longer excommunicated from the church, that babies no longer went to purgatory when they perished (instead they simply died), and finally that a Saturday mass would be instituted. The church said that it was a matter of convenience to have a Saturday mass since everyone could not attend on Sunday. However, those pursuing the matter were satisfied with the decision since the sabbath could now be faithfully observed on Saturdays.

Saturday (hi-noon) - Sunday (hi-noon):
This position comes from the understanding of the word "even" and when the "evening" actually occurs. The Day (or daylight) and Night (or darkness) are typically understood to be when the Sun is present or absent from the sky.

GEN 1:5 And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.

Note, a complete day includes FIRST the "evening" and THEN the "morning." But when one says it's 3:00 in the morning, or 5:00 in the evening, you observe the morning to be from 12:00 midnight until 12:00 hi- noon, and the evening is from 12:00 hi-noon until 12:00 midnight. From this, one determines "even" actually begins as the Sun begins to go down from it's highest point in the day (i.e. 12:00 hi-noon), rather than saying even begins after the Sun has gone down over the horizon. Thus, some practice that the Sabbath begins at hi-noon and ends at hi-noon.

Sunday:
Most present-day church goers (i.e. Baptists, Methodist, etc) attend services on Sunday and typically consider it as their day of rest, however relatively few set it aside and treat it as a hallowed day.

Tuesday (for 1995):
This day is determined from one, if not two sources. The first determination is arrived at by when the vernal equinox occurs and all the Sabbaths are then keyed off of it for that year. Another determination deals with the Julian Calendar, established in the Roman Empire by Julius Caesar (hence "Julian") in 46 B.C.. In 1582 ten days were dropped from the Julian Calendar. October 4, 1582 was a Thursday and the next day was October 15, 1582 a Friday. There was no October 5-14 of 1582. With 10 days being stripped out of the calendar, is the day we now label "Tuesday" actually a Saturday according to the Calendar of before 1582?

SO WHO/WHAT SHOULD I BELIEVE?

In closing, you should study the scriptures for yourself and conclude when to observe the Sabbath. If you decide to keep the Sabbath holy and agree upon when to observe it, remember in:

COL 2:16 Let no man therefore judge you in meat, or in drink, or in respect of an holyday, or of the new moon, or of the sabbath days.

This can be construed in two ways. One is: Don't let others rebuke you for when you have chosen to observe the Sabbath. The other, and really quite opposite, is: Don't be judged (or called in question) by any man in your meat, drink, or respect of an holyday, or of the new moon, or of the sabbath days.

[Recognize that one who is being judged has been caught, or at least accused of some wrong doing.]

Pray and resolve which interpretation you consider accurate. Lastly, don't harbor a closed mind on the point either, instead come as a child. Be open to explanations about things by others, and continue to draw nigh to the LORD for his guidance on the matter so you may discover the truth.
See and read Hosea 4:6.

[Note: All scripture quotes were from the 1611 King James Version.]