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Date
and Time
We were asked numerous
times by quite a few of our clients to create a set of reusable
macro functions to handle date and time calculations and here
they are.
The functions are all based on
Julian Day numbers, which are not to be confused with
Julian Dates, whose calendar ended on October 15th, 1582 when
the Gregorian calendar replaced it. This is the calendar in
common use today. The Gregorian calendar is a reformed Julian
calendar with the year fixed at 365 days except for leap years
which contain 366 days. Leap years are years that are exactly
divisible by 4 except for century years which must also be divisible
by 400. Dates in the Gregorian calendar are called Gregorian
dates, numbers are called Julian Day numbers. Here are some
dates and their equivalent Julian Day number.
March 1st, 0000 as far back as
these functions go 1721120
January 1st, 0001 first day of the 1st century 1721426
October 15th, 1582 first day of Gregorian calendar 2299161
November 16th, 1858 nothing special, just the Julian Day 2400000
February 28th, 1900 last day of month, not a leap year 2415079
January 1st, 1901 first day of the 20th century 2415386
January 1st, 2001 first day of the 21st century 2451911
December 31st, 9999 as far into the future as we go 5373484
We were only able to cover
a span of (almost) 10,000 years from March 1, 0000 through December
31, 9999. The Date and Time category is comprised of thirty-three
functions.
{ DateTime - Date to Julian }
Converts a date string to a Julian Day number
{ DateTime - Julian to Date } Converts a Julian Day number to
a date string
{ DateTime - Go Months } Calculates a new date based on the
number of months input
{ DateTime - Go Days } Calculates a new date based on the number
of days input
{ DateTime - Span Days } Calculates the span, or number, of
days between two dates
{ DateTime - Julian to DOY } Converts a Julian Day number to
a numeric day-of-year
{ DateTime - Date to DOY } Converts a date to a numeric day-of-year
{ DateTime - DOY to Date } Converts a year and a numeric day-of-year
to a date string.
{ DateTime - Julian to DOW } Converts a Julian Day number to
a numeric day-of-week
{ DateTime - Date to DOW } Converts a date to a numeric day-of-week
{ DateTime - Julian to Character DOW } Converts a Julian Day
number to a character day-of-week
{ DateTime - Date to Character DOW } Converts a date to a character
day-of-week
{ DateTime - Character DOW } Converts a day-of-week number to
a character day-of-week
{ DateTime - Character Month } Converts a month number to a
character month
{ DateTime - Evaluate for Leap Year } Evaluates a year to determine
if it is a leap year
{ DateTime - Format Input String } Converts a date string to
a formatted date string (YYYMMDD)
{ DateTime - Validate Date String } Performs a validation check
on an input date string
{ DateTime - Validate Julian Number } Performs a validation
check on a Julian Day number
{ DateTime - Parse Day from Date } Returns the DD part of a
date string as an integer
{ DateTime - Parse Day from Julian } Returns the day-of-month
from a Julian date
{ DateTime - Parse Month from Date } Returns the MM part of
a date string as an integer
{ DateTime - Parse Month from Julian } Returns the month from
a Julian date
{ DateTime - Parse Year from Date } Returns the YYYY part of
a date string as an integer
{ DateTime - Parse Year from Julian } Returns the year from
a Julian date
{ DateTime - Parse Day from Today } Returns the DD part of today
as an integer
{ DateTime - Parse Month from Today } Returns the MM part of
today as an integer
{ DateTime - Parse Year from Today } Returns the YYYY part of
today as an integer
{ DateTime - Today to DOW } Converts today to a numeric day-of-week
{ DateTime - Today to Character DOW } Converts today to a character
day-of-week
{ DateTime - Today to DOY } Converts today to a numeric day-of-year
{ DateTime - Today to Julian } Converts today to a Julian Day
number
{ DateTime - Reset Defaults } Resets the Date and Time values
back to their default values
{ DateTime - Set Defaults } Interactively set the Date and Time
default values
Examples
{ DateTime Example - Character DOW }
{ DateTime Example - Date to Char DOW }
{ DateTime Example - Date to DOW }
{ DateTime Example - Date to DOY }
{ DateTime Example - Date to Julian }
{ DateTime Example - DOY to Date }
{ DateTime Example - Evaluate for Leap Year }
{ DateTime Example - Go Days }
{ DateTime Example - Go Months }
{ DateTime Example - Julian to Date }
{ DateTime Example - Span of Days }
{ DateTime Example - Today Calculations }
Next: String
Functions
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