It is important to recognize how a day is measured in the Bible in order to know how and when to celebrate the Sabbath. In those days, they did not have clocks to measure time, so they had to follow nature. A day was measured starting at sunset and ending at sunset the following evening. Very different than how we measure it today (midnight to midnight). See also the Creation story, Genesis 1:5.
Please look below the graphic for references to scriptures.
Leviticus 23:32
32 It is a sabbath of rest for you, and you must deny yourselves. From the evening of the ninth day of the month until the following evening you are to observe your sabbath."
Deuteronomy 16:6
6 except in the place he will choose as a dwelling for his Name. There you must sacrifice the Passover in the evening, when the sun goes down, on the anniversary of your departure from Egypt.
Nehemiah 13:19
19 When evening shadows fell on the gates of Jerusalem before the Sabbath, I ordered the doors to be shut and not opened until the Sabbath was over. I stationed some of my own men at the gates so that no load could be brought in on the Sabbath day.
Mark 1:21-32
Jesus Drives Out an Evil Spirit
21 They went to Capernaum, and when the Sabbath came, Jesus went into the synagogue and began to teach. 22 The people were amazed at his teaching, because he taught them as one who had authority, not as the teachers of the law. 23 Just then a man in their synagogue who was possessed by an evil spirit cried out, 24 "What do you want with us, Jesus of Nazareth? Have you come to destroy us? I know who you are--the Holy One of God!" 25 "Be quiet!" said Jesus sternly. "Come out of him!" 26 The evil spirit shook the man violently and came out of him with a shriek. 27 The people were all so amazed that they asked each other, "What is this? A new teaching--and with authority! He even gives orders to evil spirits and they obey him." 28 News about him spread quickly over the whole region of Galilee.
Jesus Heals Many
29 As soon as they left the synagogue, they went with James and John to the home of Simon and Andrew. 30 Simon's mother-in-law was in bed with a fever, and they told Jesus about her. 31 So he went to her, took her hand and helped her up. The fever left her and she began to wait on them. 32That evening after sunset the people brought to Jesus all the sick and demon-possessed.