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

Day and month option
Date conversion functions:

Fractional date (YYYY.yy)

date(year,month,day)

 

Convert (Year,Month,Day) to Fractional date
Extract from a fractional date:

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:

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
Date conversion functions:

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:

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:

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

  • Tooltips that include an argument and short descriptive name are provided for each tab item.

    • 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 Julian, Gregorian, and the Roman Indiction calendars.

    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);

    See Also: