﻿ Calendar History -- Converting From the Julian Period Date

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## Converting From the Julian Period Day

From a given Julian Period Day, you can compute the values of these below.

### Converting to Other Period Days

To convert from the Julian Period Day to the Gregorian Period Day...

Julian Period Day − 38

GPD = JPD - 38

### Converting to Years of The Julian and Periods

To convert from the Julian Period Day to the Julian Period (not the Julian-1) Year...

Julian Period Day ÷ 365.25

JPY = JPD / 365.25

To convert from the Julian Period Day to the Julian-1 (not the Julian Period) Year...

(Julian Period Day ÷ 365.25) − 4712

Julian-1-Year = (JPD / 365.25) - 4712

To convert from the Julian Period Day to the Gregorian Period (not the Gregorian of the Christian Era) Year...

(Julian Period Day − 38) ÷ 365.24218967

GPY = (JPD - 38) / 365.24218967

To convert from the Julian Period Day to the Gregorian (not the Gregorian Period) Year...

((Julian Period Day − 38) ÷ 365.24218967) − 4712

Gregorian-Year = ((JPD - 38) / 365.24218967) - 4712

Note: the results for computing the Gregorian Calendar Year and the Gregorian Calendar Day of the Year may not always match the actual day of the year used on the Gregorian (Christian Era) calendar for the Julian Period Day that the Gregorian date is associated with.

### Converting to Days of the Years of The Julian and Other Periods

The idea is to use the decimal portion of the quotient and turn it into a day. Create a formula that doesn't require dividing and remultplying to get an answer for that method would result in being off a day. Example: dividing three into one, then remultiplying it by three results in 0.9999999, not one. This causes problems with obtaining an accurate answer. Instead, I created these formulas.

If you want to count up from the first day of the year with Day one instead of Day zero, just add one to the answer.

To convert from the Julian Period Day to the Julian Period (not the Julian-1) Day of The Year...

Julian Period Day − (INT(Julian Period Day ÷ 365.25) × 365.25)

JPDY = JPD - (INT(JPD / 365.25) * 365.25)

To convert from the Julian Period Day to the Julian-1 (not the Julian Period) Calendar Day of The Year...

Use the same formula above since the years for both the Julian Period and Julian-1 calendars change years on the same date.

To convert from the Julian Period Day to the Gregorian Period (not the Gregorian of the Christian Era) Day of The Year...

INT(Julian Period Day − 38) − (INT((Julian Period Day − 38) ÷ 365.24218967) × 365.24218967))

GPDY = (JPD - 38) - (INT((JPD - 38) / 365.24218967) * 365.24218967))

To convert from the Julian Period Day to the Gregorian (not the Gregorian Period) Day of The Year...

Use the same formula above since the years for both the Gregorian Period and Gregorian Era calendars change years on the same date.

Note: the results for computing the Gregorian Calendar Year and the Gregorian Calendar Day of the Year may not always match the actual day of the year used on the Gregorian (Christian Era) calendar for the Julian Period Day that the Gregorian date is associated with.

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