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Module:Keppel date/doc: Difference between revisions

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:If <code>ydayPre</code> is less than zero, subtract one.
:If <code>ydayPre</code> is less than zero, subtract one.
;<code>ydayPre</code>
;<code>ydayPre</code>
:<math>\frac{\text{ydayMax} * (\text{yday} - \text{rolloverOffset})}{\text{ydayMaxEarth}}</math>
:<math mode="display">\frac{\text{ydayMax} * (\text{yday} - \text{rolloverOffset})}{\text{ydayMaxEarth}}</math>
;<code>yday</code>
;<code>yday</code>
:<math>\text{ydayPre} \pmod{\text{ydayMaxEarth}}</math>
:<math mode="display">\text{ydayPre} \pmod{\text{ydayMaxEarth}}</math>
:If <code>yday</code> is between zero (inclusive) and one (exclusive), then <code>yday</code> is <code>ydayMax</code>.
:If <code>yday</code> is between zero (inclusive) and one (exclusive), then <code>yday</code> is <code>ydayMax</code>.
;<code>lythryd</code>
;<code>lythryd</code>
:<math>\lceil \frac{\text{yday}}{32} \rceil</math>
:<math mode="display">\lceil \frac{\text{yday}}{32} \rceil</math>
;<code>day</code>
;<code>day</code>
:<math>\lfloor \text{yday} - \text{lythryd} * 32 \pmod{32} \rfloor</math>
:<math mode="display">\lfloor \text{yday} - \text{lythryd} * 32 \pmod{32} \rfloor</math>


<includeonly>[[Category:Modules: tesinormed]]</includeonly>
<includeonly>[[Category:Modules: tesinormed]]</includeonly>

Revision as of 21:47, March 4, 2025

Converts the current (or provided) date to a Keppel date. Used by Template:Keppel date.

Algorithm

Begin with the following inputs:

year
The current year in the Gregorian calendar.
yday
The current day of the year in the Gregorian calendar.

First, we define the following:

ydayMaxEarth
If it is an Earth leap year, 366; else, 365.
ydayMax
Start with 389.
If it is an Earth leap year, add one.
If it is a Keppel leap year (schedule 1), add one.
If it is a Keppel leap year (schedule 2), add one.
rolloverOffset
If it is an Earth leap year, 79; else, 78.

To calculate the result:

year
Start with the current year minus 892.
If ydayPre is less than zero, subtract one.
ydayPre
\frac{\text{ydayMax} * (\text{yday} - \text{rolloverOffset})}{\text{ydayMaxEarth}}
yday
\text{ydayPre} \pmod{\text{ydayMaxEarth}}
If yday is between zero (inclusive) and one (exclusive), then yday is ydayMax.
lythryd
\lceil \frac{\text{yday}}{32} \rceil
day
\lfloor \text{yday} - \text{lythryd} * 32 \pmod{32} \rfloor