5 ms·

No one is mentioning calendars, and that calendars haven't been consistent enough for 1200 years to make the claim being made in the article. Here are a couple

No one is mentioning calendars, and that calendars haven't been consistent enough for 1200 years to make the claim being made in the article. Here are a couple of articles I found that show that the claim of knowing that this year's cherry blossom is "one day earlier" than one in the 1400s is pretty difficult, if not impossible, to substantiate. https://web.archive.org/web/20070402230356/http://www2.gol.com/users/stever/calendar.htm https://web.archive.org/web/20070402230356/http://www2.gol.c... https://en.wikipedia.org/wiki/Japanese_calendar https://en.wikipedia.org/wiki/Japanese_calendar

luming 6y ago
it's taken into consideration. it's not difficult to recalculate the dates. it's been done for most other anniversaries for historical events.
- prometheus76 6y ago
  Where did you find their process for recalculating the dates? The Japanese calendar was lunar and calculated locally until the 1600s in some areas, all the way up to the 1800s in other areas. How did the researchers line up the dates in the journals to astronomical data? How can they assume that when a Japanese journal said "first day of spring" that they actually meant the astronomical first day of spring, for example? I'd like to see the methodology the researchers used, but I didn't find anything in their paper about it.
  - bgee 6y ago
    > The Japanese calendar was lunar and calculated locally until the 1600s in some areas Isn't the Japanese calendar Lunisolar and borrowed from China? (from the wikipedia link you posted above)
    - prometheus76 6y ago
      "After that, Japan calculated its calendar using various Chinese calendar procedures" also from the wikipedia article. This is all just illustrating my point further.
  - Retric 6y ago
    Astronomical events like eclipses get recorded and can be extrapolated backwards to precisely line up historic calendars. Similarly, major events like huge earthquakes can be correlated between different historic calendars. Eventually you go back far enough and this breaks down, but we are talking recent history here.
    - prometheus76 6y ago
      You're assuming the researchers used earthquakes or astronomical events to correlate their date calculations, but they make no such claim. They do not explain their methodology for converting the historical calendar dates into Gregorian dates at all. Why should we give them the benefit of the doubt? They've included their dataset, but they haven't included their methodology for determining the Gregorian dates, yet their whole claim is that the dates are getting earlier and earlier. The line trending down also correlates with Japan converting to the Gregorian calendar in 1868. Why isn't that mentioned in their paper? If their methodology for converting historical dates is faulty or poor, that methodology could also account for the line appearing to move down starting in the mid-1800s. They should be transparent about it and they weren't, and a lot of people here seem to be willing to just trust them and their methodology, but I can't figure out what's scientific or transparent about that. Isn't peer review supposed to catch and correct these types of issues before publication? And if not, shouldn't they be transparent enough in sharing their methodology that the concerns raised by amateur idiots like myself would be easily addressed, or at least accounted for?
      - Retric 6y ago
        These are hardly the first researches to want to correlate Japan’s dates with the Gregorian calendar. If you think the historic record is so wrong then feel free to do some original research and prove it, but don’t assume people are idiots. Anyway, you have clearly already decided the issue in your own mind and are looking to justify it. So, no I am not going to waste my time providing evidence you can look up if you’re willing to consider the possibility you’re wrong then dare to do it yourself.
        6y ago
  - luming 6y ago
    https://www.jstage.jst.go.jp/article/timestudies/1/0/1_17/_article/-char/ja https://www.jstage.jst.go.jp/article/timestudies/1/0/1_17/_a... This is the paper. It did describe the challenges of inferring the full-bloom date from old literary work. But the calendar conversion is not one of the challenges.
    - prometheus76 6y ago
      By everything I've read, it should be included as a challenge, and they should be explicit about the method they used to determine the Gregorian dates, because it's not straightforward, nor is there even an agreed-upon method or table to use for conversion, yet their whole claim rests on the verifiability of the dates.
      - luming 6y ago
        https://rnavi.ndl.go.jp/research_guide/entry/theme-honbun-400108.php https://rnavi.ndl.go.jp/research_guide/entry/theme-honbun-40... This is a list of material and conversion tables composed by the National Diet Library on the old calendars. There are clearly well-established method and researches about this. This would be the most basic problem for anyone studying history in Japan. It may be not straightforward (for you), but it certainly would be too generic and elementary for other historians to read in a paper like this.
        prometheus76 6y ago
        If this is what they used, why didn't they say that? I'm not making a claim about what method they used. I'm saying that whatever method they used is prone to error and should be included in the methodology of the paper. What is wrong with being transparent about their methodology? And what is wrong with expecting that level of transparency in a scientific paper making a specific claim?
        prometheus76 6y ago
        I have to admit, the passive-aggressive ad hominem attacks caught me by surprise, but my request for transparency with regard to the methodology they employed when converting their dates stands.
- jhugo 6y ago
  > it's taken into consideration Since the paper doesn’t say this, I assume you’re one of the researchers or associated with them? Do you mind sharing some details about how it’s taken into consideration?
  - serf 6y ago
    the paper[0] mentions two other papers that go through the process of recreating the data and synchronizing it to the Gregorian calendar. here's one of them : https://link.springer.com/article/10.1007/s00484-009-0272-x https://link.springer.com/article/10.1007/s00484-009-0272-x [0]: http://atmenv.envi.osakafu-u.ac.jp/aono/kyophenotemp4/ http://atmenv.envi.osakafu-u.ac.jp/aono/kyophenotemp4/
    - prometheus76 6y ago
      They only state that they took the dates from old records and converted them to Gregorian dates. They do not say what method they used to convert the dates, and as noted here http://www.yukikurete.de/nengo_chronology.htm http://www.yukikurete.de/nengo_chronology.htm, old historical Japanese dates are not reliable and cannot be considered astronomically accurate. This whole paper is written assuming the dates in old records correspond to the Gregorian calendar, and that's simply not the case. The historical Japanese calendar suffered from drift away from seasonal events because the months had either 29 or 30 days in them, but the actual lunar calendar is 29.53... days long. This was a known problem, and they would occasionally add a 13th month to the year to compensate, but this was only done when either the Emperor died, or when the Emperor said to do it (usually to commemorate some significant battle). Both of those situations means that the leap months were not added in a systematic way, so trying to back-calculate dates has errors. Several attempts have been made over the last 75 years by scholars to create conversion tables for this, but they all have errors and can be inaccurate up to 4 weeks.
  - luming 6y ago
    I am not associated with the research group. I tend to think that a group of paleo-climatology professors would remember that their country used to having different calendars.
twobitshifter 6y ago
Is it possible that the timekeeping accuracy may explain the tightening of the distribution towards today? There’s a definite trend towards earlier blossoming, but you can also see that variability is decreasing.
prometheus76 6y ago
I have done more research on the Japanese calendar, and it's as I suspected: claiming to know the accuracy of a historical calendar down to the day is impossible, because the traditional calendar was primarily lunar based, but they had to add an extra month to the year occasionally because the year would start to drift away from the seasons, but this wasn't done in a consistent, systematic manner. I found a tool that attempts to back-convert Japanese dates into Gregorian dates. The tool is called NengoCalc. There's a page (in German) here http://www.yukikurete.de/nengo_chronology.htm http://www.yukikurete.de/nengo_chronology.htm that talks about the challenges of the historical Japanese calendar. Here's a quote from the google-translate version of that page: "In Japan, the Gregorian calendar was introduced in the early Meiji period. The following applies: ５明治 12 月 3 日 corresponds to 1.1.1873. Before that, the bound lunar calendar from China was used. With this the new moon falls on the first of the month. There are months with 29/30 days. From time to time intercalendar months were added, which were named after the previous month. In the case of Japan, it is particularly difficult because this did not happen regularly and therefore there was no continuous time base and consequently no continuous year counting. Instead, you have the system of annual currencies, era names, 年号. These can be changed at any time, e.g. September 1615: 慶長 20 年 -> 元和１年. The first currency of the year was 大化 (645). Because of the lunar calendar, the annual currency year can have a time difference of 4-8 weeks to the Gregorian calendar, so you need appropriate tables for conversion. So it can be that at the end of an annual currency year in the Gregorian calendar you are already in the following year. At this point it should also be pointed out that in Japanese materials this fact is often not taken into account and simply incorrect information is given. Since 1868 there has only been one currency per reign. If the annual currency changes, the year is named after the new currency. In addition, this is also used as a posthumous name for the emperor." The tool NengoCalc, uses three different tables that have been developed for converting the dates and shows the discrepancies between those tables, and tries to use the "most correct" one, but verifying the dates is impossible. All of this is to say that making claims about "this is happening on the earliest day ever" is a good headline, but scientifically unverifiable because there's no way to tie the dates in Japanese historical records to an astronomical calendar.
- Retric 6y ago
  That’s only going to provide an off by exactly one lunar month adjustment to the dates rather than say a 4 day difference. As these dates are from the same period each year it’s very solid evidence when months where added to the calendar as being 2 months out of sync would be extremely noticeable. Anyway, feel free to look for a valid possible earlier day.
yongjik 6y ago
I think it's not as hard as it initially seems. Lunar calendars are based on the shape of the moon, and we can compute past phases of the moon with sufficient accuracy. So, if the record said "cherry blossoms peaked at the tenth day of the second month, year X", then the only remaining question is when the "second month" started. Each lunar month is 29 or 30 days long, so if we miscalculate the month then the error will be also 29/30 days, back or forth. However, the graph in the article shows that almost all dates fall in (modern calendar) April. So, if the blossoms peaked at 4/20 and we miscalculate by one month, we'll arrive at 3/21 or 3/22, which is too early to be likely. Ditto in the other direction. So, even in the worst case, we can safely assume that most of the dates shown are correct (or maybe one day off, due to disagreement over when the new moon started). In addition, if they were meticulous enough to record cherry blossoms, I'd assume that the Japanese Imperial court would have written how many months were in each year ...
- prometheus76 6y ago
  Please see my other comment. I did further research and the problem comes because of drift. The lunar calendar would drift away from astronomical events, and this was a known problem, so they would occasionally add a 13th month to a year, but it wasn't done systematically. Also, there have been several attempts among scholars to create conversion tables for dates, and each of them have errors, sometimes up to 4 weeks. So which table did the researchers use? We don't know. And all of the conversion tables have errors, which brings me to my original point: making a claim that "this year is the earliest day of blossoming since the 800s in Japan" is scientifically unverifiable, because we cannot link historical calendar dates to current gregorian dates accurately before 1863, when Japan converted to the gregorian calendar.
  - labawi 6y ago
    We do not need a generalized date mapping function to verify the claim, we only need to verify specific events/dates, and even for those we only need to verify a single inequality. OTOH, looking at the data, events are dispersed over more than a month (range 124 - 86 = 38 days), so it is possible an earlier date was pushed later, where it fits better - one cannot reliably deduce month from year + day of month.
haltingproblem 6y ago
Thank you for taking the time and effort to post your comments. You exemplify quality commentary on HN which make the time spent here worthwhile. Have you thought of composing your thoughts in this thread into article and posting it on Medium/somewhere? I would be happy to give it a proofread if you write it up. Contact details in DM.
gradschoolfail 6y ago
your point is moot. The BBC article itself makes a clear statement that the claimed phenomenon is post 1800. (I cant say the same about the clickbait title of course) Presumably the drift would be so small that even without jesuit and chinese reform the effect would not be wiped out by noise.
- prometheus76 6y ago
  If they used shoddy methods for converting the dates prior to Japan converting to the Gregorian calendar in 1863, then it's absolutely relevant to their claim and could undermine their normalized trendline. If the dates are consistently 1-2 weeks off because they used a poor method for converting historical Japanese calendar dates to Gregorian dates, the line they drew normalizing their data would change significantly, and the BBC wouldn't have an article worthy of a headline. I don't understand why so many people are dismissing the calendar issue and just assuming that "it's accounted for" or "it's not relevant" or "it's trivial" or "it's just noise". Where's the transparency? They've shared their dataset, but not the method used to determine the dates? That looks like a huge oversight and so many people here seem to be accepting the premise of the claim and giving the benefit of the doubt to the researchers. What's scientific about that?
mam2 6y ago
So what ? the trend is getting earlier anyway
- prometheus76 6y ago
  If you read my other comments, you'll see that this issue could undermine their whole claim.

luming 6y ago

it's taken into consideration. it's not difficult to recalculate the dates. it's been done for most other anniversaries for historical events.

prometheus76 6y ago
Where did you find their process for recalculating the dates? The Japanese calendar was lunar and calculated locally until the 1600s in some areas, all the way up to the 1800s in other areas. How did the researchers line up the dates in the journals to astronomical data? How can they assume that when a Japanese journal said "first day of spring" that they actually meant the astronomical first day of spring, for example? I'd like to see the methodology the researchers used, but I didn't find anything in their paper about it.
- bgee 6y ago
  > The Japanese calendar was lunar and calculated locally until the 1600s in some areas Isn't the Japanese calendar Lunisolar and borrowed from China? (from the wikipedia link you posted above)
  - prometheus76 6y ago
    "After that, Japan calculated its calendar using various Chinese calendar procedures" also from the wikipedia article. This is all just illustrating my point further.
- Retric 6y ago
  Astronomical events like eclipses get recorded and can be extrapolated backwards to precisely line up historic calendars. Similarly, major events like huge earthquakes can be correlated between different historic calendars. Eventually you go back far enough and this breaks down, but we are talking recent history here.
  - prometheus76 6y ago
    You're assuming the researchers used earthquakes or astronomical events to correlate their date calculations, but they make no such claim. They do not explain their methodology for converting the historical calendar dates into Gregorian dates at all. Why should we give them the benefit of the doubt? They've included their dataset, but they haven't included their methodology for determining the Gregorian dates, yet their whole claim is that the dates are getting earlier and earlier. The line trending down also correlates with Japan converting to the Gregorian calendar in 1868. Why isn't that mentioned in their paper? If their methodology for converting historical dates is faulty or poor, that methodology could also account for the line appearing to move down starting in the mid-1800s. They should be transparent about it and they weren't, and a lot of people here seem to be willing to just trust them and their methodology, but I can't figure out what's scientific or transparent about that. Isn't peer review supposed to catch and correct these types of issues before publication? And if not, shouldn't they be transparent enough in sharing their methodology that the concerns raised by amateur idiots like myself would be easily addressed, or at least accounted for?
    - Retric 6y ago
      These are hardly the first researches to want to correlate Japan’s dates with the Gregorian calendar. If you think the historic record is so wrong then feel free to do some original research and prove it, but don’t assume people are idiots. Anyway, you have clearly already decided the issue in your own mind and are looking to justify it. So, no I am not going to waste my time providing evidence you can look up if you’re willing to consider the possibility you’re wrong then dare to do it yourself.
      - 6y ago
- luming 6y ago
  https://www.jstage.jst.go.jp/article/timestudies/1/0/1_17/_article/-char/ja https://www.jstage.jst.go.jp/article/timestudies/1/0/1_17/_a... This is the paper. It did describe the challenges of inferring the full-bloom date from old literary work. But the calendar conversion is not one of the challenges.
  - prometheus76 6y ago
    By everything I've read, it should be included as a challenge, and they should be explicit about the method they used to determine the Gregorian dates, because it's not straightforward, nor is there even an agreed-upon method or table to use for conversion, yet their whole claim rests on the verifiability of the dates.
    - luming 6y ago
      https://rnavi.ndl.go.jp/research_guide/entry/theme-honbun-400108.php https://rnavi.ndl.go.jp/research_guide/entry/theme-honbun-40... This is a list of material and conversion tables composed by the National Diet Library on the old calendars. There are clearly well-established method and researches about this. This would be the most basic problem for anyone studying history in Japan. It may be not straightforward (for you), but it certainly would be too generic and elementary for other historians to read in a paper like this.
      - prometheus76 6y ago
        If this is what they used, why didn't they say that? I'm not making a claim about what method they used. I'm saying that whatever method they used is prone to error and should be included in the methodology of the paper. What is wrong with being transparent about their methodology? And what is wrong with expecting that level of transparency in a scientific paper making a specific claim?
      - prometheus76 6y ago
        I have to admit, the passive-aggressive ad hominem attacks caught me by surprise, but my request for transparency with regard to the methodology they employed when converting their dates stands.
jhugo 6y ago
> it's taken into consideration Since the paper doesn’t say this, I assume you’re one of the researchers or associated with them? Do you mind sharing some details about how it’s taken into consideration?
- serf 6y ago
  the paper[0] mentions two other papers that go through the process of recreating the data and synchronizing it to the Gregorian calendar. here's one of them : https://link.springer.com/article/10.1007/s00484-009-0272-x https://link.springer.com/article/10.1007/s00484-009-0272-x [0]: http://atmenv.envi.osakafu-u.ac.jp/aono/kyophenotemp4/ http://atmenv.envi.osakafu-u.ac.jp/aono/kyophenotemp4/
  - prometheus76 6y ago
    They only state that they took the dates from old records and converted them to Gregorian dates. They do not say what method they used to convert the dates, and as noted here http://www.yukikurete.de/nengo_chronology.htm http://www.yukikurete.de/nengo_chronology.htm, old historical Japanese dates are not reliable and cannot be considered astronomically accurate. This whole paper is written assuming the dates in old records correspond to the Gregorian calendar, and that's simply not the case. The historical Japanese calendar suffered from drift away from seasonal events because the months had either 29 or 30 days in them, but the actual lunar calendar is 29.53... days long. This was a known problem, and they would occasionally add a 13th month to the year to compensate, but this was only done when either the Emperor died, or when the Emperor said to do it (usually to commemorate some significant battle). Both of those situations means that the leap months were not added in a systematic way, so trying to back-calculate dates has errors. Several attempts have been made over the last 75 years by scholars to create conversion tables for this, but they all have errors and can be inaccurate up to 4 weeks.
- luming 6y ago
  I am not associated with the research group. I tend to think that a group of paleo-climatology professors would remember that their country used to having different calendars.

twobitshifter 6y ago

Is it possible that the timekeeping accuracy may explain the tightening of the distribution towards today? There’s a definite trend towards earlier blossoming, but you can also see that variability is decreasing.

prometheus76 6y ago

I have done more research on the Japanese calendar, and it's as I suspected: claiming to know the accuracy of a historical calendar down to the day is impossible, because the traditional calendar was primarily lunar based, but they had to add an extra month to the year occasionally because the year would start to drift away from the seasons, but this wasn't done in a consistent, systematic manner. I found a tool that attempts to back-convert Japanese dates into Gregorian dates. The tool is called NengoCalc. There's a page (in German) here http://www.yukikurete.de/nengo_chronology.htm http://www.yukikurete.de/nengo_chronology.htm that talks about the challenges of the historical Japanese calendar. Here's a quote from the google-translate version of that page: "In Japan, the Gregorian calendar was introduced in the early Meiji period. The following applies: ５明治 12 月 3 日 corresponds to 1.1.1873. Before that, the bound lunar calendar from China was used. With this the new moon falls on the first of the month. There are months with 29/30 days. From time to time intercalendar months were added, which were named after the previous month. In the case of Japan, it is particularly difficult because this did not happen regularly and therefore there was no continuous time base and consequently no continuous year counting. Instead, you have the system of annual currencies, era names, 年号. These can be changed at any time, e.g. September 1615: 慶長 20 年 -> 元和１年. The first currency of the year was 大化 (645). Because of the lunar calendar, the annual currency year can have a time difference of 4-8 weeks to the Gregorian calendar, so you need appropriate tables for conversion. So it can be that at the end of an annual currency year in the Gregorian calendar you are already in the following year. At this point it should also be pointed out that in Japanese materials this fact is often not taken into account and simply incorrect information is given. Since 1868 there has only been one currency per reign. If the annual currency changes, the year is named after the new currency. In addition, this is also used as a posthumous name for the emperor." The tool NengoCalc, uses three different tables that have been developed for converting the dates and shows the discrepancies between those tables, and tries to use the "most correct" one, but verifying the dates is impossible. All of this is to say that making claims about "this is happening on the earliest day ever" is a good headline, but scientifically unverifiable because there's no way to tie the dates in Japanese historical records to an astronomical calendar.

Retric 6y ago
That’s only going to provide an off by exactly one lunar month adjustment to the dates rather than say a 4 day difference. As these dates are from the same period each year it’s very solid evidence when months where added to the calendar as being 2 months out of sync would be extremely noticeable. Anyway, feel free to look for a valid possible earlier day.

yongjik 6y ago

I think it's not as hard as it initially seems. Lunar calendars are based on the shape of the moon, and we can compute past phases of the moon with sufficient accuracy. So, if the record said "cherry blossoms peaked at the tenth day of the second month, year X", then the only remaining question is when the "second month" started. Each lunar month is 29 or 30 days long, so if we miscalculate the month then the error will be also 29/30 days, back or forth. However, the graph in the article shows that almost all dates fall in (modern calendar) April. So, if the blossoms peaked at 4/20 and we miscalculate by one month, we'll arrive at 3/21 or 3/22, which is too early to be likely. Ditto in the other direction. So, even in the worst case, we can safely assume that most of the dates shown are correct (or maybe one day off, due to disagreement over when the new moon started). In addition, if they were meticulous enough to record cherry blossoms, I'd assume that the Japanese Imperial court would have written how many months were in each year ...

prometheus76 6y ago
Please see my other comment. I did further research and the problem comes because of drift. The lunar calendar would drift away from astronomical events, and this was a known problem, so they would occasionally add a 13th month to a year, but it wasn't done systematically. Also, there have been several attempts among scholars to create conversion tables for dates, and each of them have errors, sometimes up to 4 weeks. So which table did the researchers use? We don't know. And all of the conversion tables have errors, which brings me to my original point: making a claim that "this year is the earliest day of blossoming since the 800s in Japan" is scientifically unverifiable, because we cannot link historical calendar dates to current gregorian dates accurately before 1863, when Japan converted to the gregorian calendar.
- labawi 6y ago
  We do not need a generalized date mapping function to verify the claim, we only need to verify specific events/dates, and even for those we only need to verify a single inequality. OTOH, looking at the data, events are dispersed over more than a month (range 124 - 86 = 38 days), so it is possible an earlier date was pushed later, where it fits better - one cannot reliably deduce month from year + day of month.

haltingproblem 6y ago

Thank you for taking the time and effort to post your comments. You exemplify quality commentary on HN which make the time spent here worthwhile. Have you thought of composing your thoughts in this thread into article and posting it on Medium/somewhere? I would be happy to give it a proofread if you write it up. Contact details in DM.

gradschoolfail 6y ago

your point is moot. The BBC article itself makes a clear statement that the claimed phenomenon is post 1800. (I cant say the same about the clickbait title of course) Presumably the drift would be so small that even without jesuit and chinese reform the effect would not be wiped out by noise.

prometheus76 6y ago
If they used shoddy methods for converting the dates prior to Japan converting to the Gregorian calendar in 1863, then it's absolutely relevant to their claim and could undermine their normalized trendline. If the dates are consistently 1-2 weeks off because they used a poor method for converting historical Japanese calendar dates to Gregorian dates, the line they drew normalizing their data would change significantly, and the BBC wouldn't have an article worthy of a headline. I don't understand why so many people are dismissing the calendar issue and just assuming that "it's accounted for" or "it's not relevant" or "it's trivial" or "it's just noise". Where's the transparency? They've shared their dataset, but not the method used to determine the dates? That looks like a huge oversight and so many people here seem to be accepting the premise of the claim and giving the benefit of the doubt to the researchers. What's scientific about that?

mam2 6y ago

So what ? the trend is getting earlier anyway

prometheus76 6y ago
If you read my other comments, you'll see that this issue could undermine their whole claim.