That little outfit called NASA says this:
The Persian Calendar, also known as the Iranian Calendar, is made available in a similar fashion for it is the most accurate of calendars. These calendars are included for the millions of people who use them regularly.
But this is quite complicated, as the term "accuracy" for a calendar might mean quite different things, depending on definitions or applications. So:
Is There A Perfect Calendar?
The simple answer is no.
Persian calendar –– invented in 2nd millennium BCE –– 365.2421986 days Less than 1 sec/year (1 day in 110,000 years)
Revised Julian calendar –– 1923 CE –– 365.242222 days 2 sec/year (1 day in 31,250 years)
Mayan calendar –– ~2000 BCE –– 365.242036 days 13 sec/year (1 day in 6500 years)
Gregorian calendar –– 1582 CE –– 365.2425 days 27 sec/year (1 day in 3236 years)
The Revised Julian Calendar –– 10 Times More Accurate
Wikipedia: Revised Julian calendar
Trpković advocated this calendar in preference to the Gregorian because of its greater accuracy and also because the vernal equinox would generally fall on 21 March, the date allocated to it by the church. In the Gregorian, it generally falls on 20 March. As in the Gregorian, end-century years are generally not leap years, but years that give remainder 0 or 400 on division by 900 are leap years. The changeover went into effect on 17 February/1 March.
Even the original Gregorian calendar had its proposed reforms:
The Gregorian calendar improves the approximation made by the Julian calendar by skipping three Julian leap days in every 400 years, giving an average year of 365.2425 mean solar days long. This approximation has an error of about one day per 3,030 years with respect to the current value of the mean tropical year. However, because of the precession of the equinoxes, which is not constant, and the movement of the perihelion (which affects the Earth's orbital speed) the error with respect to the astronomical vernal equinox is variable; using the average interval between vernal equinoxes near 2000 of 365.24237 days implies an error closer to 1 day every 7,700 years. By any criterion, the Gregorian calendar is substantially more accurate than the 1 day in 128 years error of the Julian calendar (average year 365.25 days).
In the 19th century, Sir John Herschel proposed a modification to the Gregorian calendar with 969 leap days every 4000 years, instead of 970 leap days that the Gregorian calendar would insert over the same period. This would reduce the average year to 365.24225 days. Herschel's proposal would make the year 4000, and multiples thereof, common instead of leap. While this modification has often been proposed since, it has never been officially adopted. (WP: Gregorian calendar) [Although this is closer to the mean tropical year of 365.24219 days, his proposal has never been adopted because the Gregorian calendar is based on the mean time between vernal equinoxes (currently 365.242374 days).]
Mädler's correction proposal has almost been forgotten. However, his proposal for calendar regulation can hardly be surpassed in its exactness due to the insignificant difference to the tropical year.
The Maedler calendar system would become even more accurate during the 20th and 21st centuries and reached its optimum in 2033 (according to VSOP87 and 2048). According to the newer VSOP2000, the length of the tropical year decreases by about half a second per century. This means that with continued switching according to Gregorian switching rule the calendar would have shifted after 3231 years (thus in the year 2803) already in relation to the astronomical starting point in the year 1582 by one day. The primary equinox would then take place permanently one day earlier. With schematic-extrapolative application of the Mädler switching rule, however, a need for correction (insertion of an additional leap day) would only be expected 331,126 years after its introduction.
For a simple observation that the original claim is just a misleading oversimplification, the above should be enough.
The Gregorian calendar is quite accurate and relatively easy to handle. This makes for an almost elegant solution, which is probably what the claimant meant. But it is by far not an ideal calendar and there have been systems devised before and after the Gregorian that are on this single scale "accuracy" a better choice. Different calendars were devised to solve different problems. The Gregorian calendar solves the problem of having the Christian holiday of Easter reliably in spring time and relative to the related equinox. It's nice to see the hyperbole of "is the most accurate ever devised" from the claimant praising a pope and his computus aware mathematicians for their concern of religious matters.
That almost none of the efforts of improving on it since goes unnoticed in the claim is lamentable. That none of the ideas of metrification, that is basing this measurement of time on natural constants – like it was done for meter and second – is even considered necessary seems quite curious.
We now use the Gregorian calendar for other reasons –– and have to make the odd adjustment to its proscriptions from time to time, like leap-seconds. It seems advisable for people concerned with just the progression of time as measured in real solar days to use an intermediate representation from the plain Julian day calendar, from 1583:
Julian day is the continuous count of days since the beginning of the Julian Period and is used primarily by astronomers, and in software for easily calculating elapsed days between two events (e.g. food production date and sell by date) The Julian Day Number (JDN) is the integer assigned to a whole solar day in the Julian day count starting from noon Universal time, with Julian day number 0 assigned to the day starting at noon on Monday, January 1, 4713 BC, proleptic Julian calendar (November 24, 4714 BC, in the proleptic Gregorian calendar), a date at which three multi-year cycles started (which are: Indiction, Solar, and Lunar cycles) and which preceded any dates in recorded history. For example, the Julian day number for the day starting at 12:00 UT on January 1, 2000, was 2 451 545.
The Julian date (JD) of any instant is the Julian day number plus the fraction of a day since the preceding noon in Universal Time. Julian dates are expressed as a Julian day number with a decimal fraction added. For example, the Julian Date for 00:30:00.0 UT January 1, 2013, is 2 456 293.520 833.
The Julian Period is a chronological interval of 7980 years; year 1 of the Julian Period was 4713 BC. It has been used by historians since its introduction in 1583 to convert between different calendars. The Julian calendar year 2018 is year 6731 of the current Julian Period. The next Julian Period begins in the year AD 3268.
If you are interested in more detail for a comparison of accuracy, advantages and disadvantages among calendar systems, you might want to read Kalender - Computus. Or continue to read below:
For example, the Iranian solar calendar is systematic and quite accurate, but has constant switching rules. Therefore, the question remains whether the Gregorian calendar can be simplified and better adapted to our lives today.
As has already been said, one goal could be to avoid or reduce the error of the Gregorian solar year, which means that another leap day has to be omitted in the 4th year dew. One could therefore change the switching rules, e.g. by not all century years divisible by 400 remaining leap years, as is currently the case, but only those whose number of years divided by 9 gives the remainder 2 or 6. So 2000 and 2400 would be leap years as before, but then not 2800, but only 2900, not 3200, but 3300, not 3600, but 3800, etc. All other century years are normal years with 365 days. This reform year of the Oriental churches was decided in 1923 by the Congress of these churches in Constantinople, chaired by Patriarch Meletius IV, and was to be introduced in Russia, Greece, Serbia and Romania. Since the date should be corrected by 13 days and Easter should no longer be determined cyclically but astronomically according to the meridian of Jerusalem, this reform would also be acceptable for the Western churches, especially since differences will only occur from 2800 in the solar year.
Unfortunately, this has not yet been introduced because, on the one hand, resistance against the change of date arose in the Eastern Churches, as celebrations for up to 13 day saints would be affected. On the other hand, however, the astronomical calculation method offers counter-arguments, because now one is again dependent on the correct calculation of an institution and its distribution of the official full moon data. Both the leap second of the previous passage and this full moon indication would use a modern Pope Maximus as in ancient Rome or an Easter letter writer as in the time of early Christianity.
No wonder then that no agreement has yet been reached on this proposal. However, the adoption of the new switching rule would have the advantage that the duration of the solar year would be reduced to 365 d 5 h 48 m 48 s. This is 24 seconds better than the Gregorian year, leaving only a residual error of 2 customers, which would only add up to one error day after about 40,000 years. Unfortunately, however, this switching rule is not as easy to remember as the rule of the century up to now. Furthermore, it has the disadvantage that now 1600 should not have been a leap year!
A suggestion by J.H. Mädler (1794-1874), with which he wanted to reduce the errors of the Gregorian calendar[Sele 81], should be mentioned at this point. With a chain fracture development of the length of the solar year it received the approximation 365 31/128 d, thus 365.242 19 d. This means the use of 31 leap days in 128 years and would have the advantage that an error of one day would not accumulate for more than 100,000 years. If it had been introduced in 1900, it would have been 2028, 2156, etc. Normal years without leap day, during 2100, 2200 etc. leap years remained. But this could not be achieved in the 19th century. Only in our days does an operational cycle of 128 = 27 years no longer seem so strange.
Another proposal for a future calendar tries to make the quarters the same length, e.g. 13 weeks with 7 days, i.e. 91 days, resulting in 364 days as the length of the year. The 365th (aand possibly 366th) day would be celebrated as a holiday (New Year, leap year) and removed from the continuous weekday count. Then all data would be bound to their weekday, would be repeated quarterly, but the length of the month would have to be changed so that twice 30 and once 31 days per quarter occur. For Easter too, a fixed Sunday would have to be specified, for example the first Sunday in April, i.e. 7 April, when the year thus reformed begins with a Monday. Despite numerous debates, it was not possible to overcome the resistance, especially since all traditionalists are now in the same camp: to interrupt the continuation of the weekday count, to redefine the length of the month, to set up the additional celebration days (31.12. and 31.6. of a new kind) and to fix all movable celebrations, that is simply too much!
So we will stick to the Gregorian calendar for the foreseeable future. Is it therefore not useful to have read and experienced something about its meaning in the world, its origin, its structure and its problems? At least we know some not so obvious oddities and curiosities with which we are used to live.
Winfried Görke: "Datum und Kalender – Von der Antike bis zur Gegenwart", Springer: Heidelberg, Dordrecht, 2011. (p 149–150.)
Since Mr Tyson is not quoted out of context, and the content of the quote is "not true", it needs a further qualification to become "true". Perhaps: "the Gregorian calendar is the most accurate calendar ever devised" –
–– by the Catholic church.
–– that was actually adopted for wide spread use in the Western dominated world.