Traditionally, 'Good' Friday has been assumed to be the day of the week that Jesus was crucified, using such passages as Mark 15:42-43, since 'preparation day' was taken to mean 'Friday', and 'Sabbath' was taken to mean 'Saturday':

It was Preparation Day (that is, the day before the Sabbath). So as evening approached, Joseph of Arimathea, a prominent member of the Council, who was himself waiting for the kingdom of God, went boldly to Pilate and asked for Jesus' body.

However, there is evidence in the bible that the 'Last Supper' the Jesus ate with his disciples was not the Jewish 'Passover' feast, as is traditionally claimed.  There is also corresponding evidence that the 'Crucifixion' of Jesus did not occur on ('Good') Friday.  While these are not critical issues, they are nevertheless intereresting to consider.

Jesus prophesied that he would be dead for 3 days and 3 nights

Jonah 1:17

But the LORD provided a great fish to swallow Jonah, and Jonah was inside the fish three days and three nights.

Matthew 12:40

For as Jonah was three days and three nights in the belly of a huge fish, so the Son of Man will be three days and three nights in the heart of the earth.

My Comments: There have been various attempts to re-interpret the terms "three days and three nights" into non-literal 24-hour time periods (or even periods of day-light and night-darkness, but it would seem to be impossible to make a Friday afternoon crucifixion and Sunday morning resurrection fit into this prophecy.

The Last Supper was not the Passover

John 13:27-30

As soon as Judas took the bread, Satan entered into him. "What you are about to do, do quickly," Jesus told him, but no one at the meal understood why Jesus said this to him. Since Judas had charge of the money, some thought Jesus was telling him to buy what was needed for the Feast, or to give something to the poor. As soon as Judas had taken the bread, he went out. And it was night.

John 18:28

Then the Jews led Jesus from Caiaphas to the palace of the Roman governor. By now it was early morning, and to avoid ceremonial uncleanness the Jews did not enter the palace; they wanted to be able to eat the Passover.

My Comments: Judas evidently had more errands to run in preparation for the 'feast' (of Passover), even while the 'last supper' was wrapping up.  This suggests that the 'last supper' was not the passover.  The next day (during the trials of Jesus), the Jewish religious leaders also were looking forward to the 'Passover' -- which had evidentally not yet occured.  

The Crucifixion took place on the Preparation day for the Passover

John 19:31

Now it was the day of Preparation, and the next day was to be a special Sabbath. Because the Jews did not want the bodies left on the crosses during the Sabbath, they asked Pilate to have the legs broken and the bodies taken down.

Mark 15:42-43

It was Preparation Day (that is, the day before the Sabbath). So as evening approached, Joseph of Arimathea, a prominent member of the Council, who was himself waiting for the kingdom of God, went boldly to Pilate and asked for Jesus' body.

Matthew 27:62

The next day, the one after Preparation Day, the chief priests and the Pharisees went to Pilate.

Matthew 28:1

Early on Sunday morning, as the new day was dawning, Mary Magdalene and the other Mary went out to visit the tomb.

Luke 24:1,13,21

On the first day of the week, very early in the morning, the women took the spices they had prepared and went to the tomb...Now that same day two of them were going to a village called Emmaus, about seven miles from Jerusalem... And what is more, it is the third day since all this took place.

My Comments: Jesus was crucified on the 'day of preparation' (for the Passover), and the next day was a 'special' Sabbath (not the ordinary 'Saturday' Sabbath).  The Matthew 28:1 reference to 'Sunday morning' is actual the plural form of the word 'Sabbath' i.e. σάββατον (sabbaton), suggesting that there were two Sabbaths that week.  The Luke references which say that Sunday (Resurrection Day) is the 'third day since all of this took place' i.e. the Crucifixion Day.

Jesus is the Passover Lamb

1 Corinthians 5:7

Get rid of the old yeast that you may be a new batch without yeast--as you really are. For Christ, our Passover lamb, has been sacrificed.

My Comments: If Jesus was (figuratively and literally) the 'Passover Lamb' (and He was!) then it makes sense that he would have died at the same time as all the lambs were being killed/prepared for the Passover.

Jesus was resurrected before sunrise on Sunday

John 20:1

Early on the first day of the week, while it was still dark, Mary Magdalene went to the tomb and saw that the stone had been removed from the entrance.

My Comments: The 'first day of the week' is Sunday, and Jesus was resurrected before daylight on Sunday morning.  Jesus was dead for three days (Thursday afternoon, Friday, Saturday) and for three nights (Thursday night, Friday night, Saturday night). He fulfilled his own prophecy.

IVP New Testament Commentary on these issues

John 19 Commentary

The Jewish opponents refuse to enter the praetorium to avoid ceremonial uncleanness (v. 28). There is no law in the Old Testament against entering a Gentile's home, but in later teaching it is laid down that "the dwelling-places of gentiles are unclean" (m. Oholot 18:7; cf. Brown 1994:1:745; Beasley-Murray 1987:327). The opponents sought to avoid defilement because they wanted to be able to eat the Passover (v. 28). Since Jesus has already eaten with his disciples a meal that the Synoptics say was the Passover (Mt 26:17 par. Mk 14:12 par. Lk 22:8; 22:15), this verse raises questions. Many interpreters argue either that John has shifted the chronology in order to have Jesus dying at the very time the Passover lambs are being sacrificed--making the point dramatically that he is the Lamb of God who takes away the sin of the world (for example, Lindars 1972:444-46; Barrett 1978:48-51)--or that his chronology is historically accurate (especially Brown 1994:2:1351-73; cf. Robinson 1985:147-51) and therefore the meal he shared with his disciples was not Passover.

Others have attempted to maintain that the meal in all four Gospels is the Passover. One solution suggests that John is referring here not to the Passover meal itself, but to the Feast of Unleavened Bread, a week-long celebration that took place in conjunction with it. This longer celebration can be referred to as Passover, as it is, for example, in Luke: "Now the Feast of Unleavened Bread, called the Passover, was approaching" (22:1; cf. Josephus Antiquities of the Jews 14.21). These Jewish opponents, then, wish to be able to take part in the seven-day feast about to begin (cf. Carson 1991:589; Ridderbos 1997:457). Alternatively, some suggest that "John has in mind the lunchtime meal known as the chagigah, celebrated during midday after the first evening of Passover" (Blomberg 1987:177). But although the term Passover may be applied to the whole sequence, including the Feast of Unleavened Bread, the expression "eat the Passover" is not a natural way to refer to keeping the whole feast nor to eating the chagigah, but rather a way to refer to the Passover meal specifically. For example, the references in the Synoptics just cited use exactly the expression here (esthio to pascha) to speak of sharing in the Passover meal. Furthermore, there is no evidence the term Passover was used to refer to the Feast of Unleavened Bread apart from the Passover itself (Morris 1971:778-79, but cf. Blomberg 1987:177 n. 2).

Another solution to the discrepancy is that different calendars were followed. The main calendar used was a lunisolar calendar, but some groups, apparently including the community at Qumran, used a solar calendar of 364 days (cf. Schürer 1973-1987:1:587-601; Vanderkam 1992). The main drawback to this solution is the lack of evidence for Jesus' having followed the solar calendar (cf. Vanderkam 1992:820). The other main proposal is that the Galileans and the Pharisees reckoned days from sunrise to sunrise, while Judeans did so from sunset to sunset. This means the Judeans, including these opponents, would slaughter their lambs late Friday afternoon, whereas Jesus and his disciples had theirs slaughtered late Thursday afternoon (Hoehner 1977:83-90; cf. Morris 1971:782-85). It has also been suggested that the slaughtering of the lambs actually took place over two days because of the volume of lambs involved (Hoehner 1977:84). According to these solutions, Jesus has already eaten Passover, but the opponents have yet to do so. A major drawback to theories of different days for celebrating Passover is "the lack of any hint of such a distinction in the gospels themselves" (Blomberg 1987:176-77).

My Comments: Different interpretations of these events are possible!

Suggested Crucifixion Week Chronology

The Narrated Bible in Chronological Order by F. LeGard Smith (1984)

Traditionally the last supper is believed to have occurred on Thursday evening, followed by the crucifixion on Friday afternoon and the resurrection on Sunday morning.  However, such reckoning raises at least two questions.  First, in an action-packed final week, what reason is there to believe that there would be a whole day of either actual inactivity or activity which is left unrecorded?  Second, and far more important - If Jesus is crucified on Friday afternoon and thereafter hurriedly put into the tomb, how can there be sufficient time to match Jesus' own prediction that He would remain in the tomb for three days and three nights before being resurrected?

The resolution of both questions appears to be found in recognizing that the last supper took place on Wednesday evening, followed by the crucifixion and burial on Thursday.  Acceptance of that assumption requires an understanding of the Passover, the Feast of Unleavened Bread, and the way in which the Jews reckon time.  As for the reckoning of time, the Jewish day begins at sunset on the previous evening.  This means, for example that our Wednesday night is actually Thursday, and our Thursday night is actually Friday.

Passover is observed on the 14th day of the month of Nisan, corresponding to March-April...The Passover is followed by the seven-day Feast of Unleavened Bread...By God's direction (Leviticus 23), a lamb is to be slaughtered late on the 14th day (Passover) and the Passover meal eaten that evening, which would be the beginning of the 15th day, the first day of the Feast of Unleavened Bread.  The entire 15th day is then to be observed as a special Sabbath, or high holy day, regardless of the day of the week on which it might fall in any given year. (If the 15th day is a Friday, then both that Friday and the next day, Saturday, are observed as Sabbaths.)...

John's account eliminates any doubt that this supper occurred prior to the actual Passover meal.  When Jesus tells Judas during the supper to do what he is about to do, some of the other disciples "thought Jesus was telling him to buy what was needed for the Feast."  Furthermore, the Jews who have obtained Jesus' arrest will not enter Pilate's palace for fear that they will be ceremonially unclean, and therefore unable to eat the Passover.  Most convincing is the fact that the day of Jesus' crucifixion is plainly stated to be "the day of Preparation of Passover Week" - the day on which the paschal lamb is slain for the Passover meal taken during the evening of that day.

The most meaningful result of moving away from the traditional timeframe is seeing how Jesus' crucifixion becomes the perfect "type" of the Passover Lamb.  Under Hebrew law, the paschal lamb is chosen on the tenth day and then "kept up" until the 14th day, when it is sacrificed for the sins of the people.   If Jesus' triumphant entry into Jerusalem is counted as the tenth day, Thursday would be the 14th day, and thus the day on which Jesus is crucified.  Far more important than this possible parallel is the fact that Jesus, as the perfect Lamb of God, does not celebrate the Passover with some other ordinary sacrificial lamb, but rather becomes Himself the Lamb who is slain - precisely at the appropriate hour!

There is therefore strong evidence that the last supper takes place on the evening prior to the Day of Preparation, which by modern reckoning would be Wednesday night (1454-1456).

Evangelical Commentary on the Bible edited by Walter A. Elwell (1989)

The Passover Meal (John 13:1-30). The Synoptics record that during his last week of ministry, during the Passover festival, Jesus enjoyed a final meal with his disciples (Mark 14:12-25).  Each synoptic writer terms this "the Passover" (Matt. 26:17; Mark 14:12; Luke 22:7-9) ordinarily served after dusk on the Jewish date of 15 Nisan.  John mentions such a meal (13:2,26) and indicates through mention of the betrayal of Judas (13:21-30) that this meal is the synoptic Passover (cf. Mark 14:17-21).  However, John's date cannot be 15 Nisan (Passover) for later he will say that Jesus is crucified on 14 Nisan when the temple lambs are being slaughtered (19:14).  Hence the Johannine record shows the meal to be on the Day of Preparation, on night prior to the Passover feast.

Scholars have solved this riddle in a variety of ways.  The easiest and most popular solution is simply to say that one Gospel tradition or the other is incorrect.  But critics can find fault with each account: Would the Sanhedrin hold a trial on a feast day as the Synoptics contend?  Or has John moved the cross to 14 Nisan to develop a paschal emphasis for Jesus' death (cf. 19:32-37)?  Recent studies have urged that both narratives might be accurate due to competing calendars in the first century.  Hence ceremonial meals may have been sponsored on more than on night during the festival week.

How Close Are We by Dare Hunt (1993)

[Chapter 16: Forget "Good Friday": When Was The "Last Supper" and the Crucifixion? (p168)]

Mark says, "Now when the even [i.e., sunset was approaching] was come [after Christ had died], because it was the preparation [of the Passover lamb], that is, the day before the sabbath [the first day of the Feast of Unleavened Bread, which began at sunset after the Passover lamb had been slain], Joseph of Arimathaea ... went in boldly unto Pilate, and craved the body of Jesus" (15:42,43). Luke agrees: "And that day was the preparation, and the [special] sabbath drew on" (23:54). John gives even more detail:

Then led they [the rabbis] Jesus from Caiaphas unto the [Roman] hall of judgment ... and they themselves went not into the judgment hall, lest they should be defiled; but that they might eat the Passover [so it hadn't been eaten as yet]. And it was the preparation of the Passover... The Jews therefore, because it was the preparation, that the bodies should not remain upon the cross on the sabbath day (for that sabbath day was an high day [i.e., the first day of unleavened bread]), besought Pilate that their legs might be broken, and that they might be taken away (John 18:28; 19:14,31).

So, as we noted in the last chapter, the Passover lambs were indeed being slain at the very time that Christ, the Lamb of God who fulfilled all of the relevant Old Testament types and prophecies, died on the cross. How, then, could Christ have "taken the Passover" with His disciples the night before? He didn't. The Last Supper did indeed occur the night before the crucifixion, but it was not the Passover. This often overlooked fact is clear from John's account, which is a bit more precise.

While the other gospels refer to "the sabbath" drawing nigh, John alone explains that the sabbath which began at sunset the day Christ was crucified "was a high day." In other words, it was not the ordinary weekly sabbath which always began Friday at sunset. It was, in fact, the first day of the Feast of Unleavened Bread (the fifteenth of Nisan), of which the first and last days were special sabbaths during which no work was to be done (Exodus 12:14-16).

John also clarifies the fact that the "last supper" was not the Passover: "Now before the feast of the Passover, when Jesus knew that his hour was come ... supper being ended, the devil having now put into the heart of Judas Iscariot ... to betray him." So the "last supper" actually took place the night before the Passover. How could it have taken place both "the first day of unleavened bread" and "before the feast of the Passover"?

Although technically the Feast of Unleavened Bread began with the fifteenth of Nisan after sunset of the fourteenth (the Passover lamb was slain just before sunset, roasted, and eaten that night), the days of unleavened bread were also counted from the fourteenth of Nisan because the eating of unleavened bread began "on the fourteenth day of the month at evening" (Exodus 12:18). Though they were two separate feasts, the Passover and Feast of Unleavened Bread were treated as one inasmuch as they overlapped. The Passover lamb, though "prepared" (i.e., slain and the roasting process begun) just before sunset on the fourteenth, was not eaten until that night, which was then the fifteenth.

What day of the week was Nisan 14? While we refer to Nisan 10 as Sunday, it began on Saturday after sunset when the sabbath ended. Remember, the Jewish day begins at sunset. Thus Nisan 11 began at sunset Sunday, the twelfth Monday, the thirteenth Tuesday, and Nisan 14, the day of preparation, began Wednesday at sunset. The "last supper," then, took place Wednesday night, the beginning of Nisan 14, which was called the day of preparation. The following afternoon, in the "evening" of Nisan 14, the Passover lambs were slain shortly before sunset. Christ was on the cross and "gave up the ghost" at the same time that Thursday afternoon.

Thursday? Not "Good Friday"? Indeed not. A Friday crucifixion doesn't fit the facts. Not only the prophecies but the Old Testament types as well had to be fulfilled. One of those types was known as "the sign of the prophet Jonas [Jonah]." It required Jesus to be in the grave "three days and three nights."

Wikipedia Chronology of Jesus

According to John, however, the Passover meal was to be eaten on the last evening before Jesus was crucified, so that the Last Supper was eaten on the evening of 14th of Nisan and the crucifixion was on the 14th, at the same time that the lambs for the Passover were being slaughtered in Herod's Temple of Jerusalem, so that the Jews could celebrate the Passover that evening (starting Friday night). Various attempts have been made to harmonize the two reports. Perhaps the most likely theory is that Jesus, knowing he was to be dead at the appointed time for the Passover meal, chose to hold the Passover meal with his disciples a day early, thus holding to the account of John. Some scholars have recently suggested rejecting Thursday as the day of the Last Supper and support a non-Passover Last Supper on Tuesday or Wednesday, thus providing more time for the events that occurred between the Last Supper and the Crucifixion.

According to Orthodox theology, the Last Supper celebrated on Thursday evening was not the Jewish Passover meal. This can be seen from the Biblical text itself since Jesus gave a piece of (leavened) bread to Judas, which would have been a direct violation of Jewish Passover regulations, also since, as the article mentions, Jesus dies the next day at the same time that the Passover lambs are slaughtered (no Passover meal without Passover lamb). Instead, Jesus as God's Passover Lamb puts an end to the old and institutes a new concept, the Christian Eucharist.

Evidence to the contrary...Friday Crucifixion

Mathew 26:17

On the first day of the Feast of Unleavened Bread, the disciples came to Jesus and asked, "Where do you want us to make preparations for you to eat the Passover?"

Mark 14:12

On the first day of the Feast of Unleavened Bread, when it was customary to sacrifice the Passover lamb, Jesus' disciples asked him, "Where do you want us to go and make preparations for you to eat the Passover?"

Luke 22:7-8

Then came the day of Unleavened Bread on which the Passover lamb had to be sacrificed.  Jesus sent Peter and John, saying, "Go and make preparations for us to eat the Passover."

My Comments: These three other writers place the Passover on the same day as the Last Supper.

Evidence to the contrary...Wednesday Crucifixion