Telling time - sunset to sundown, new moon to new moon - was later specificied to the Hebrews in Exodus et cetera. Sundown to sundown was defined as a day, new moon to new moon as a month.
You may not be able to find the sun at 1am (even though that time is a Roman chronology,) but I bet you notice a difference between day covering and night covering, or the breaking through of that covering to have a difference in the firmament.
I used to think the Jews were right in the calendar, until I read the Book of Enoch and the Dead Sea Scrolls....
The Calendar God established is still in force and can never change, but men have changed it, even the Jews did, when they returned from Babylon....
The day indeed begins at sunset, but the new moon never determines the beginning of the month, and the translaions err when they translate month as moon.
The sun's entry into the established paths [electromagnetic portals of entry in it's circle of the earth in the circle of the heavens] begin the seasons, and the months are calculated by the sun's rising and setting in the eastern to north eastern and back to eastern and then to the south eastern and back to the eastern to make make one full year of 360 days, counted with their parts [we call then hours, and we are off], with the four stop days [not counted with hours/parts] and 364 numbered days to a year. The year forever has 364 days, but only the four days are never numbered in the weeks of the year, and the years always beginn at Spring Solstice for religious year, and Fall Solstice for number of years since creation..
The Sun's portal entries establish the months and the years. The DSS Essenes separated themselves from the Pharisees in Jerusalem for one reason of a dispute on the calendar....even they set the fourth day as the beginning of the year, but they were in error there also, as it begins at Spring Equinox for religious year, and fall equinox for numbered years from creation.
There are exactly 360 days in God's calendar as revealed by Enoch, and four "stop/Sabbath" days that are not numbered in the days of the week days in the year, but the four "stop" days are added in number of days to a year at the end of the year, but they never have a counted week day, as to the weeks.
Because the days are counted in "parts" in God's universal never changing calendar, and the parts are lengthened and shortened as to light and darkness, through the year, the "parts" of the four "stop/Sabbath days" are never counted in the calendar God ordains, so the year always comes exactly to 360 days/ 52 weeks, and the four stop/sabbath days added to the number of days in the year make a year 360 exact days, from the beginning to eternity, says Enoch, and Enoch says men will [and have] erred as to the years when they do not calculate them by God's revealed calendar, established in the heavens.
So Equinox from the center of the earth [God's stated navel/midst of the earth =Mount Zion] begins the counting of the year's days, and the numbering of the year's weeks, and because the stops/sabbaths are not counted, every festival or anniversary of any event returns on the same day of the week each year, in God's calendar.
So, men err, but God will set it all right when Jesus/Yeshua returns to reign.