Date Tab
Use the Date tab to select the appropriate date function, which enables you to convert to, or from, a fractional date vs. Julian date or extract date information from a fractional date. For more information, see the Application Notes below.
Date Tab options
Button |
Syntax |
Definition |
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Day and month option |
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Date conversion functions: |
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Fractional date (YYYY.yy) |
date(year,month,day) |
Convert (Year,Month,Day) to Fractional date |
Extract from a fractional date: |
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Year (YYYY) |
date_year(fractional date) |
Extract Year from Fractional date |
Month (MM) |
date_month(fractional date) |
Extract Month from Fractional date |
Day (DD) |
date_day(fractional date) |
Extract Day from Fractional date |
Convert date: |
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Fractional date (YYYY.yy) |
date_from_long(days) |
Convert Julian date to Fractional date |
Julian date (DDDD) |
date_to_long(fractional date) |
Convert Fractional date to Julian date |
Day of year option |
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Date conversion functions: |
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Fractional date (YYYY.yy) |
date_from_day_of_year(year,day_of_year) |
Convert (Year, Day of the year) to Fractional date |
Extract from a fractional date: |
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Year (YYYY) |
date_year(fractional date) |
Extract Year from Fractional date |
Day of the year (DY) |
date_day_of_year(fractional date) |
Extract Day of the year from Fractional date |
Convert date: |
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Fractional date (YYYY.yy) |
date_from_long(days) |
Convert Julian date to Fractional date |
Julian date (DDDD) |
date_to_long(fractional date) |
Convert Fractional date to Julian date |
Application Notes
Fractional Date
The Fractional date (or fractional years) can be calculated from Year, Month, Day. Alternatively it can be converted from Year and Day of the year. A simple algorithm to calculate the fractional years using the current number of days and the total number of days in that year (taking into account leap years) is: Year + (days/total_days_in_year).
Julian Date
Use the date_to_long(fractional date) function to convert a fractional date to a Julian date. The Julian Date is typically used when dealing with days, for arithmetic date manipulation. The new date can be converted back into a fractional date.
The beginning of the Julian time (time 0 on day 0 of year 0) is at 12:00 (noon) on 1 January, 4713 BCE. This is when the three calendrical cycles converged, namely the
The most common calendrical days used in computation however are Epoch days, the beginning of which is midnight on 01/01/1970. To account for the difference between noon on 01/01/-4713 and midnight on 01/01/1970, add 2440587.5 days to the Epoch days in the conversion equation:
Julian_date = date_from_long(Epoch_days+2440587.5);
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