Lobsang

Lobsang deals with Julian / Gregorian calendar issues given specific geographic locations and the Time at which they switched between using either calendar system.

Nomen est omen

• https://wiki.lspace.org/mediawiki/Lobsang_Ludd
• https://wiki.lspace.org/mediawiki/Time

Background hints

On start-of-year:

• https://en.wikipedia.org/wiki/Old_Style_and_New_Style_dates
• https://en.wikipedia.org/wiki/Calendar_(New_Style)_Act_1750
• https://en.wikipedia.org/wiki/Julian_calendar#New_Year's_Day

Examples:

• Given a date "March 24, 1751" sourced somewhere in England, when was this on the Gregorian calendar we use today?

  $ curl -s localhost:8080/convert -H 'Content-type: application/json' \
         -d '{"targetCalendar": "gregorian", \
              "year": "1751", "month": "3", "day": "24",
              "place": "england"}' | jq -C .
  {
    "dates": [
      {
        "year": 1752,
        "month": 4,
        "day": 4,
        "notes": [
          "Based on data for place: 'England and Wales'",
          "Date after 1 January, but in this period, new year started on 03-25, so one year was added.",
          "Date on or before end of Julian calendar"
        ]
      }
    ]
  }
  

  Answer: 4 April 1752.

  Because in 1751, the New Year started on March 25th (as opposed to January 1st which we are accustomed to nowadays), the subject date of 24 March was by our current accounts actually in 1752. Also, eleven days have to be added because the Julian calendar was in effect which, at that time, was 11 days behind the Gregorian calendar.

• The execution of Charles I was recorded at the time in parliament as happening on 30 January 1648. What date would his contemporaries in parts of continental Europe have recorded his execution by?

  curl -s localhost:8080/convert -H 'Content-type: application/json' \
       -d '{"targetCalendar": "gregorian", \
            "year": "1648", "month": "1", "day": "30", \
            "place": "england"}' | jq -C .
  {
    "dates": [
      {
        "year": 1649,
        "month": 2,
        "day": 9,
        "notes": [
          "Based on data for place: 'England and Wales'",
          "Date after 1 January, but in this period, new year started on 03-25, so one year was added.",
          "Date on or before end of Julian calendar"
        ]
      }
    ]
  }
  

  Answer: 9 February 1649.

  If we wanted the date in Julian, but with the year corrected to start on 1 January, we ask for "targetCalendar": "julian" which yields the following result

  $ curl -s localhost:8080/convert -H 'Content-type: application/json' \
         -d '{"targetCalendar": "julian", \
              "year": "1648", "month": "1", "day": "30", \
              "place": "england"}' | jq -C .
  {
    "dates": [
      {
        "year": 1649,
        "month": 1,
        "day": 30,
        "notes": [
          "Based on data for place: 'England and Wales'",
          "Date after 1 January, but in this period, new year started on 03-25, so one year was added.",
          "Date on or before end of Julian calendar"
        ]
      }
    ]
  }
  

  Answer: 30 January, 1649

  As this note on Charles I explains, this is sometimes referred to as Old Style Julian calendar.