For as Jonas was three days and three nights in the whale’s belly; so shall the Son of man be three days and three nights in the heart of the earth. Matthew 12:40

Jesus plainly, on several occasions, said he would rise from the dead on the third day. Luke 9:22 Saying, The Son of man must suffer many things, and be rejected of the elders and chief priests and scribes, and be slain, and be raised the third day.

Matthew 16:21 From that time forth began Jesus to shew unto his disciples, how that he must go unto Jerusalem, and suffer many things of the elders and chief priests and scribes, and be killed, and be raised again the third day.

Matthew 17:22 And while they abode in Galilee, Jesus said unto them, The Son of man shall be betrayed into the hands of men: 17:23 And they shall kill him, and the third day he shall be raised again. And they were exceeding sorry.

Matthew 20:18 Behold, we go up to Jerusalem; and the Son of man shall be betrayed unto the chief priests and unto the scribes, and they shall condemn him to death, 20:19 And shall deliver him to the Gentiles to mock, and to scourge, and to crucify him: and the third day he shall rise again.

His apostles attested to the fact that he resurrected on the third day (Acts 10:40, 1Cor 15:4). That is he was buried on Friday, and resurrected on Sunday morning.

Even when the Jews said he had said he would resurrect after three days, they understood after three days to be on the third day. That was why they insisted that the sepulchre be secured until the third day, and not until the fourth day.

Matthew 27:63 Saying, Sir, we remember that that deceiver said, while he was yet alive, After three days I will rise again. 27:64 Command therefore that the sepulchre be made sure until the third day, lest his disciples come by night, and steal him away, and say unto the people, He is risen from the dead: so the last error shall be worse than the first.

When Jesus said in Matthew 12 :40 that he would be in the heart of the earth for three days and three nights, he was following a Hebrew idiom of speaking which means within three days. He makes this clear when he spoke proverbially concerning his resurrection in John 2:19

Jesus answered and said unto them, Destroy this temple, and in three days I will raise it up. 2:20 Then said the Jews, Forty and six years was this temple in building, and wilt thou rear it up in three days? 2:21 But he spake of the temple of his body. 2:22 When therefore he was risen from the dead, his disciples remembered that he had said this unto them; and they believed the scripture, and the word which Jesus had said.

This Hebraic way of reckoning days is elsewhere used in other parts of the Bible and other Jewish writings. For examples, in Esther 4:16, Esther who calls a fast for 3 days and 3 nights before going in to the king, goes in to the king on the 3rd day (Esther 5:1). 
In 1Samuel 30:12, an abandoned servant who said he had not eaten or drunken for 3 days and 3 nights, says in verse 13 that he was abandoned 3 days ago. In these examples ‘after 3 days and 3 nights’ is equivalent in Jewish mind to on the 3rd day. In the Jerusalem and Babylonian Talmud, a Jewish Rabbi Eleazar ben Azariah (10th from Ezra, 100AD) states that: “a day and a night are an Onah (a portion of time) and a portion of an Onah is as the whole of it.” That is, in Jewish thinking, any portion of ‘a day and a night’ is counted as one ‘day and a night.’

Those that seek to say Jesus was crucified on Wednesday would be writing a whole new account of the death of Jesus contrary to that which his apostles witness, for how can they explain the Sabbath ( which is Saturday day) being the very next day after his crucifixion.

John 19:31 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,) besought Pilate that their legs might be broken, and that they might be taken away.