I hope this is the right place to ask this question, and I apologise if not.

I've come across a date written in an old book, but it is written using what seems to be a lunar/zodiac system. Below is a picture of the date (ignore the text above it):

enter image description here

I'm trying to work out what this date would have been in our modern calendar, but I can't seem to find any tables or almanacs that go back that far.

Are there any publicly available tables that do go back to 1587? If not, how exactly could I go about calculating the answer for myself? I am a mathematician, so a bit of wacky maths should be within my capabilities. This is the answer I'm probably expecting from this site: some kind of program/algorithm/formula to be able to work out on what date the moon would have been in Taurus in

If not, any ideas as to where best for me to ask/look next?


2 Answers 2


You can calculate this using the program "KAIROS", See here: http://www.raymondm.co.uk/ It will let you play through the variables: Is this a Julian or a Gregorian date? Is it using true or mean positions? And so forth.


You probably got this far yourself, but here is my absolutely wild speculative guess on why this could be 24 May 1587 on the Gregorian calendar:

  • It seems fairly clear that this refers to the 24th of some month in 1587, but it's not as clear which month this is, and whether this is in the Gregorian or Julian calendar.

  • The moon symbol followed by the symbol for Taurus may indicate "the month where the new moon was in Taurus". This is slightly ambigious, since the new moon is was Taurus on both June 6th and May 7th, but I believe May 7th slightly is more likely for the reasons below.

  • Wikipedia notes that "cerasus" is a a dated synonym of the genus Prunus (https://en.wikipedia.org/wiki/Cerasus), which includes cherries.

  • Historically, there is no "Cherry Moon" (although there are songs, movies, and possibly more that mention it), but cherry trees are known for their flowers, so this may be a reference to the Full Flower Moon of May:


  • The word "gexia" translates to "Your Mightiness" in Chinese:


but I'm pretty sure this is red herring, since the paper doesn't appear to be in Chinese, and I'm not sure Chinese transliteration even existed at the time. However, it would fit in nicely.

  • So this could be saying "the full cherry (flower) moon occurs on 24 May 1587". Unfortunately, the actual full moon occurs late on the 22nd GMT, so the 24th is a bit of a stretch even allowing for the 16th century equivalent of "time zones"

  • The Gregorian calendar reform occurred in 1582. Many countries didn't adopt it until much later, but the text appears to be in a Latin-based language (ie, a Romance language), and countries like this were quick to switch to the Gregorian calendar:


  • If this is 24 May 1587 in the Julian calendar, it would be 10 days later, 3 Jun 1587, in the Gregorian calendar. This date seems less likely, since there is no full moon on that date, though there is almost a new moon in Taurus, so maybe.

So why would the author write "month of moon in Taurus" instead of the actual month name? It's possible he was trying to be careful, since the months would be different in the many countries still using the Julian calendar.

Of course, it may just be a reference to the lunar eclipse of 24 Mar 1587:


  • 1
    $\begingroup$ Romanians call June ciresar (cireasa means cherry). Taurus is commonly associated with late April to late May. $\endgroup$
    – Lucian
    Aug 28, 2018 at 11:40

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