Unix time. Zero is midnight UTC on 1 January 1970.

Using Jesus as a reference is unfortunate, yeah, but any other world calendars have to pick a nearly equally arbitrary way to contextualize the start and end year.

Take your pick: https://en.m.wikipedia.org/wiki/Template:Year_in_various_calendars

I personally use "2024 CE" for "common era", with BCE referring to "before common era". This allows us to communicate relatively clearly with other people who use the Gregorian calendar without explicitly endorsing the birth of Jesus as the important event defining the switch-over between CE and BCE... A bit of a cop out, but

Anyway have fun, there are lots of options

Edit: also the one you're referring to in your post is the Holocene Calendar

The start of the calendar has to be arbitrary, there's no way around that as it's not feasible to measure the time since the beginning of the universe with good enough accuracy.

As others commented, the Julian Day is a time measure that is actually used in astronomy, and Unix time is a time stamp standard (not really a calendar, although it could be if we got used to it) that is mostly a way to store time points, not really to consume them before converting to a more readable form.

But as a scientist who is wholly irreligious, I'm not overly bothered by using the Gregorian calendar, even though it has Christian (and a lot of pre-Christian) elements. Its annoyances (different numbers of days in each month, weeks not aligning with years, leap years etc.) are due to the fact that we decided to measure time in these arbitrary units. At least it's universal in the modern era (often in conjunction with another calendar), and everywhere you go people understand what "August 5, 2024" means (although August might have to be translated to the target language, since the names of the months are not universal).

That's more than you can say about non-time units of measurement (I'm looking at you, imperial and US customary units!!)

Historians don't use "BC" and "AD". Haven't for a while now.

While the arbitrary date remains the same (year zero), it's C.E. (common era) or B.C.E. (Before common era)

FYI

The YouTube Channel Kurzgesagt has proposed a calendar based on the 'Human Era' (HE) instead of before/after christ format.

It's based on the first monument of large-scale human cooperation (building a temple in modern-day turkey) and is quite elegant in my opinion. It 'simply' adds 10.000 years to the calendar we're all already used to. :)

Birth of Jesus isn't even accurate. Best guess is that, if it happened at all, which is up for debate, it was around 4 BC.

I don't think there's any way to count years without rooting it somewhere arbitrary. We cannot calculate the age of the planet, the sun, or the universe to the accuracy of a year (much less a second or nanosecond). We cannot define what "modern man" is to a meaningful level of accuracy, either, or pin down the age of historical artifacts.

Most computers use a system called "epoch time" or "UNIX time", which counts the seconds from January 1, 1970. Converting this into a human-friendly date representation is surprisingly non-trivial, since the human timekeeping systems in common use are messy and not rooted in hard math or in the scientific definition of a second, which was only standardized in 1967.

Tom Scott has an amusing video about this: https://www.youtube.com/watch?v=-5wpm-gesOY

There is also International Atomic Time, which, like Unix Time, counts seconds from an arbitrary date that aligns with the Gregorian calendar. Atomic Time is rooted at the beginning of 1958.

ISO 8601 also aligns with the Gregorian calendar, but only as far back as 1582. The official standard does not allow expressing dates before that without explicit agreement of definitions by both parties. Go figure.

The core problem here is that a year, as defined by Earth's revolution around the sun, is not consistent across broad time periods. The length of a day changes, as well. Humans all around the world have traditionally tracked time by looking at the sun and the moon, which simply do not give us the precision and consistency we need over long time periods. So it's really difficult to make a system that is simple, logical, and also aligns with everyday usage going back centuries. And I don't think it is possible to find any zero point that is truly meaningful and independent of wishy-washy human culture.

https://en.wikipedia.org/wiki/International_Fixed_Calendar

A bigger problem to solve is that depending on where you are, today is 06/08/2024, 08/06/2024, 2024-08-06 .. For. The. Same. Day.

So, can we please standardise on 2024-08-06 across the planet before we start considering what 1/1/1 is?

UNIX time uses a Julian calendar date as a reference, but is independent after that.

As for the 13 month calendar, it's about as nice as cloverleaf interchanges: appealing because it's symmetrical, terrible in practice. Having the days of the month always align to the same weekday means leap years would make things even worse because every 4 years the entire calendar shifts. And if you skip the leap day as a holiday then you just make calculating dates from an epoch like UNIX time even more convoluted.

Epoc time?

My ideal is dropping the month altogether for 13 week Quarters with the last day being an intercalary outside the week and same for leap days.

If you wanna avoid huge date numbers, break it down further by weeks, so for example my BDay this year would be 3.10.3, third day of the tenth week of the third quarter.

As for year counting, I like Era of History for the current era, dating to the invention of writing, Era of Legend, dating back 100k years to the earliest date that stories we have preserved now would have to date back to, Era of Evolution, which dates back to the development of Life on Earth, Era of Stars which dates back to the birth of the first Stars in the Universe, and finally the Era of Energy, in which the universe was so superheated that large cosmic structures were physically impossible, dating to the Big Bang.

Today's Date is 3.8.1; 5,224 EoH

Barycentric Dynamical Time is one example of an astronomical time standard used in orbital dynamics models requiring consistency across billions of years and relativistic reference frames.

Maybe a calendar that starts with the creation of the Earth (approx 4 billion years ago) as it's starting point?

Holocene Calendar is the one used by those Kurzgesagt calendars.

Maybe we are currently living in a BC era and year 0 hasn't happened yet.

https://en.m.wikipedia.org/wiki/French_Republican_calendar

https://en.m.wikipedia.org/wiki/Year_Zero_(political_notion

CE and BCE. Same thing different name. shrug

Who is this Jesus fellow? Everyone knows that today is a.d. viii Id. Aug. anno MMDCCLXXVII A.U.C.

I don't know of any books I can recommend, but I'd definitely be down for 13 months with one being short. We could do 12 months of 30 days each plus a 13th month of 5 (or on leap years 6) days.

As far as anything that exists today, there is the Unix Timestamp which is defined as the number of seconds since (the entirely arbitrary time of) midnight January 1st 1970 UTC. Of course, "1970" only makes sense in the context of the Gregorian calendar which still has to do with the birth of Jesus. So, it's not exactly what you're looking for. But maybe it's at least more removed from "the birth of Jesus" than the Gregorian calendar we all generally use.

I guess if you're interested in this stuff, you might be interested in learning about ISO-8601, a standard way of representing dates/times in text. And also the concept of "leap seconds" and things like Leap Smearing.

There's also a great short story about someone trying to explain to an alien with no familarity with earth how our calendar works, but I'm having trouble finding it now. I'll edit this post with a link if I can find it.