Time keeping is one of those things that once interested me and then I just assumed everyone knows. Like many other things time keeping has its roots in the book of Genesis.
Then God said, "Let there be lights in the expanse of the heavens to separate the day from the night, and let them be for signs and for seasons and for days and years;
NASUHumans are, at least are now, four dimensional creatures. We exist in, or at least currently access, a three dimensional universe and we progress through time. Thus 4 dimensions. Back in Genesis chapter 1, time was not a limiting factor for humans. However, it was something that we were given the ability to track and the method for tracking it was based on astronomical observation.
In the same comment thread I wrote: "I don't know if it was 6,000 years or not. I say that because I don't believe the point of the genealogies was to mark time.". I happen to believe that the years listed in the genealogies are years as we understand them today. The only difference being that they may be a 360 day year, more on that latter. I also believe that if the bible says someone lived 900 years, and had their first kid at 130 years of age, that's what happened. In other words, its literal. The point of the genealogy was to establish a pedigree, not a calendar.
Time keeping as defined by God, is not the function of genealogical record, rather it is a marking of astronomical observation. Human calendar systems reflect that. Today we measure time differently than man has historically. We do this because our modern society is largely removed from agricultural production. Today we mark minutes, hours, days of the week, months, and years. In the past people marked the day, the 7th day, the moon, and tracked the year. The reason was the seasons corresponded to things that were important to them, like planting time, harvest or favorable sailing weather. Modern time keeping is focused on keeping appointments, and maintaining a schedule that is economically functional in our culture.
It seems that a number of ancient calendars recognize a 360 day year. People began adjusting and readjusting their calendars due to the seasons being out of date with the month. I suspect that at some point in the past that the earths orbit may have been more in sync with a 360 day year. Today we utilize a 365 and 1/4 day year. Every forth year we add a day for leap year to keep the calendar lined up with solar position. Different cultures and civilizations have used different methods to accomplish the same thing.
So what about the Jews? The Jews had one of the more interesting time keeping methods. It was based on astronomical observation. The reason they had such a detailed methodology was the requirements of Mosaic Law. In order to comply with that law they made detailed astronomical observations by multiple persons every night of the year for a period of nearly 3,000 years. It has only been since the 4th century AD that they have calculated the dates mathematically. Even with that they still maintain astronomical observations. Here is some web based material I have found helpful in understanding the Jewish Method. This is a link to basic material. The section below is from the same author.
The Jewish calendar is based on three astronomical phenomena: the rotation of the Earth about its axis (a day); the revolution of the moon about the Earth (a month); and the revolution of the Earth about the sun (a year). These three phenomena are independent of each other, so there is no direct correlation between them. On average, the moon revolves around the Earth in about 29½ days. The Earth revolves around the sun in about 365¼ days, that is, about 12 lunar months and 11 days.
To coordinate these three phenomena, and to accommodate certain ritual requirements, the Jewish calendar consists of 12 or 13 months of 29 or 30 days, and can be 353, 354, 355, 383, 384 or 385 days long. The keystone of the calendar is the new moon, referred to in Hebrew as the molad.I have mentioned before that different cultures have different dating schemes. Our current calendar was set up in an effort to keep lunar time in sync with solar time. The rational for Daylight Sayings time, is basically a method to keep the mechanical clock aligned with the solar day. I'd argue that it is a meaningless exercise in our day and age.
I made mention of the Jewish calendar system because it is very old, very accurate in terms of established Biblical holidays, and because despite the fact we seldom acknowledge it, the Jews were God's people first. Gentile Christians are included into a religious system that was set up and run for centuries without us. If you want to know about Old Testament practices, you have to see what the Jews were doing.
I believe the Lord can return at anytime. This next part is conjecture and is not a theological position. According to the Jews it is 5,774 years since creation. According to the apostle Peter "a day with the Lord is as a 1,000 years and a 1,000 years as a day". According to millennialist theology there will be 7 years of tribulation followed by 1,000 years of Jesus ruling man on earth. I don't expect to be around in 219 years, but if I was, I think I'd worry about it more than the Mayan Long Form Calendar.