All four accounts use the same word when describing the day:
Now after the Sabbath (σαββάτων), toward the dawn of the first day of the week (σαββάτων)… (Matthew 28:1)
And very early on the first day of the week (σαββάτων)… (Mark 16:2)
But on the first day of the week (σαββάτων)... (Luke 24:1)
Now on the first day of the week (σαββάτων)… (John 20:1)
The meaning of the word σαββάτων is Sabbaths plural.
Rendering the word σαββάτων as “the first day of the week,” is one way of saying the day was Sunday on the weekly calendar. In Biblical terms the only day of the week which is named is the seventh day; it is called the Sabbath. The weekly Sabbath comes every Saturday on the modern calendar. All English translations choose “first day of the week” which is an interpretation of σαββάτων. A translation would be "Sabbaths."
It is possible for Sabbaths to refer to multiple weekly Sabbaths. Yet this meaning is impossible for an event which takes place after three days and three nights, which is the time Jesus spent in the tomb. Therefore the day He was resurrected (Sabbaths) cannot be referring to weekly Sabbaths.
The Feast of Unleavened Bread immediately follows the Passover and begins and ends with a day of no work:
On the first day you shall hold a holy assembly, and on the seventh day a holy assembly. No work shall be done on those days. But what everyone needs to eat, that alone may be prepared by you. (Exodus 12:16)
The “Passover” tradition became synonymous for Feast of Unleavened Bread and the “Sabbath” tradition became synonymous of a day of no work. So the Feast of Unleavened Bread also begins and ends with a "Sabbath" of rest and assembly.
The day of resurrection occurred after the Sabbath of the first day of the Feast of Unleavened Bread and after the weekly Sabbath, a point which can be found in Luke:
Then they returned and prepared spices and ointments. On the Sabbath (σάββατον - singluar) they rested according to the commandment. (Luke 23:56)
On a Sabbath (singular) “they rested according to the commandment.” The commandment is both to rest on the day after the Passover and the seventh day of week. After resting on a Sabbath the women went after the Sabbaths (plural) (Luke 24:1).
The English translations of the plural would better convey the specific date of the resurrection if it was rendered as it is written, "Sabbaths." In reality, the Day of the Resurrection was already on the annual calendar:
And the LORD spoke to Moses, saying, “Speak to the people of Israel and say to them, When you come into the land that I give you and reap its harvest, you shall bring the sheaf of the firstfruits of your harvest to the priest, and he shall wave the sheaf before the LORD, so that you may be accepted. On the day after the Sabbath the priest shall wave it. And on the day when you wave the sheaf, you shall offer a male lamb a year old without blemish as a burnt offering to the LORD. And the grain offering with it shall be two tenths of an ephah of fine flour mixed with oil, a food offering to the LORD with a pleasing aroma, and the drink offering with it shall be of wine, a fourth of a hin. And you shall eat neither bread nor grain parched or fresh until this same day, until you have brought the offering of your God: it is a statute forever throughout your generations in all your dwellings. (Leviticus 23:9-14)
Jesus died at the time of Passover and was resurrected on the day of the Feast of Fruits. These events are found on the annual calendar.
The annual calendar also has a day of rest immediately after the Passover to mark the first day of the Feast of Unleavened Bread. The weekly Sabbath will fall sometime during the seven days of Unleavened Bread. The day following this weekly Sabbath is supposed to be the Day of Firstfruits. It will come the day after the Sabbaths. Using the terminology of the annual calendar this day would be called the Day of Firsfruits; using the terminology of the weekly calendar it could be called the first day of the week.