How Do I Find Number of Days between 2 Dates? - Solved

[DR White]

How Do I Find Number of Days between 2 Dates?

So I have been beating my head against a wall for almost 3 hours, trying not to bother anyone on the forum. I looked at several instructions in the dictionary, but I have not found a way to get the number of days between 2 different dates.

Thanks,

David

[richmond62]

http://lists.runrev.com/pipermail/use-l ... 35553.html

[richmond62]

ftp://ftp.bu.edu/pub/mirrors/info-mac/_ ... -dates.hqx

You'll need a Macintosh capable of running Mac OS 9 or earlier: I'm going to have a poke
at it on my iMac G5.

[richmond62]

[FourthWorld]

Short answer:

Code: Select all

on mouseUp
   put DaysBetween("12/1/16", the date)
end mouseUp

function DaysBetween pDate1, pDate2
   -- Make sure we're working with valid date values:
   if pDate1 is not a date then
      return "First argument is not a date" for error
   end if 
   if pDate2 is not a date then
      return "Second argument is not a date" for error
   end if 
   -- Do the arithmetic with integer seconds:
   convert pDate1 to seconds
   convert pDate2 to seconds
   put abs(pDate1-pDate2) into tDiff
   -- Convert seconds to days and return it:
   return (tDiff / (60*60*24))
end DaysBetween

Long answer:
a) See Richmond's link above
b) See https://www.youtube.com/watch?v=-5wpm-gesOY

In short, you will find circumstances in which the function above will fail. Time is surprisingly complicated stuff. But most of the time it'll do what you need.

[richmond62]

Ouch: Hypercard behaving oddly under Mac OS Tiger (10.4) on my G5:

I wonder if the stack is on the different disk to the operating system?

[Lagi Pittas]

Hi

When I started using livecode the first thing I noticed was the lack of date functions I was used to in Foxpro - Yes I can write them using judicious use of date convert etc but I like my simple Foxpro calls. So the first library I wrote was date routines I had been using for the best part of 25 years.

With the seconds/zones/GMT problem I decided that I needed a reliable way to do the dates between dates routine. So I wrote a julian day number calculation base on a wikipedia article

Code: Select all

-- Julian Day Number    -- As Per http://fox.wikis.com/wc.dll?Wiki~JulianDates
-- Agrees with Wikipedia January 1, 2000, was 2,451,545.
function JDN pDate
   local  lnD, lnM, lnYr, lnJulianDate
   
   set itemdelimiter to "/"
   
   put item 1 of pDate into lnD
   put item 2 of pDate into lnM
   put item 3 of pDate into lnYr
   
   put  367  *  lnYr - TRUNC(7 * (lnYr + TRUNC ((lnM + 9) / 12)) / 4) into  lnJulianDate     
   put lnJulianDate  - TRUNC(3 * (TRUNC((lnYr + (lnM - 9) / 7) / 100) + 1) / 4) into lnJulianDate
   
   put  lnJulianDate  + TRUNC(275 * lnM / 9)     +  lnD + 1721029    into lnJulianDate
   
   Return lnJulianDate
   
end JDN

With that out of the way the days between function became trivial

Code: Select all

-- Function : DayBetween() 
-- Remarks  : If the second date is blank it will use the current systemdate
--                   :  Assumes caller knows which is before or after 
-- Params   : {Date} pDate1, {Date} pDate2
-- Returns  : {Integer} Absolute number of days (with decimals) between the two dates
Function DaysBetween pDate1, Pdate2
   local lnD1, lnD2, lnDays
   
   set the usesystemdate to true 
   
   if pDate2 is empty then
      put the system date into pDate2
   end if
   
   put JDN(pDate1) into lnD1  
   put JDN(pDate2) into lnD2
   
   put ABS(lnD1 - lnD2) into lnDays
   
   return lnDays
   
end DaysBetween

Some of the other routines are trivial but very useful nonetheless if you have been using them for over 25 years

Code: Select all

-- Function : GODAYS()
-- Remarks  : The date passed in as a parameter plus or minus the days specified.
-- param    : {Date}    pDate - Date we are adding or subtracting to/from
-- param    : {Integer} pDays - Number of days to add/substract to pDate
-- Returns  : {Date} pdDate - Date pDays forward or back
function GODAYS pDate, pDays
   
   set useSystemDate to true
   
   convert pDate to dateitems
   add pDays to item 3 of pDate
   convert pDate to system date -- NOt strictly needed but ....
   return pDate
end GODAYS

Another one used in an employee database

Code: Select all

-- Function : Age() 
-- Remarks  : Pass in a Date of Birth to Find age in years months and Days
--          : Uses Julian Number 
-- Params   : {Date} pDate1, {Date} pDate2
-- Returns  : {Integer} Absolute number of days (with decimals) between the two dates
Function Age pDOB, pUpto
   
   local lnD1,  lnD2, lnYears, lnMonths, ldToday, lnDays, lcAge
   set itemdelimiter to "/"
   put the short system date into ldToday
   
   -- Allow age calcuklation upto any date - even future
   if pUpto is not empty then
      put pUpto into ldToday
   end if
   
   -- Get the Julian date with base  January 1st 4713 BC
   put   JDN(ldToday) into lnD1
   put   JDN(pDOB)    into lnD2
   
   put TRUNC((lnD1  - lnD2) / 365.25) into lnYears
   put  TRUNC((((lnD1 - lnD2) / 365.25) - lnYears) * 12) into lnMonths
   put TRUNC( ( ((((lnD1 - lnD2) / 365.25) - lnYears) * 12) - lnMonths)  * 30.42) into lnDays -- My addition which makes it as close as dammit for the days
   
   -- Send back 3 ITEMS
   put  lnYears &  "," &  lnMonths &  ","  &  lnDays into lcAge
   
   return lcAge
   
end Age

GOMONTH() is a stock Foxpro function but GODAYS() was needed because in foxpro we can just add numbers to a date variable and it returns a day variable
-- All my routines are UK date specific -

"We don't need no steenkin timezones!"

Code: Select all

-- Function : GOMONTH()
-- Remarks  : The date passed in as a parameter plus or minus
--          : the months specified. To go forward a year pass  12 back a year -12
-- param    : {Date} pDate - Base Date to add or substract the months to
-- param    : {integer} pnMonths - Number of months to add/substract to pDate
-- Returns  : {date} pDate - Date nMonths forward or -nMonths back
function GOMONTH pDate, pMonths 
   
   -- We are passing in a string in BRITISH (UK) format not ENGISH (AMERICAN)
   -- So we tell the system that (assuming the users date is in DD/MM/YYY format
   -- This property is local and only lasts for the current handler
   set useSystemDate to true
   
   convert pDate to dateitems
   add pMonths to item 2 of pDate
   convert pDate to system date
   return pDate
   
end GOMONTH

-- Function : GODAYS()
-- Remarks  : The date passed in as a parameter plus or minus the days specified.
-- param    : {Date}    pDate - Date we are adding or subtracting to/from
-- param    : {Integer} pDays - Number of days to add/substract to pDate
-- Returns  : {Date} pdDate - Date pDays forward or back
function GODAYS pDate, pDays
   
   set useSystemDate to true
   
   convert pDate to dateitems
   add pDays to item 3 of pDate
   convert pDate to system date -- Not strictly needed but ....
   return pDate
end GODAYS

I'm sure we can make these smaller faster more beautiful - but they were written while i was learning and they work for me -

"If it ain't broke , don't fix it"

Regards Lagi

[FourthWorld]

Good use of useSystemDate to handle non-US date formats. My function should have included that. Good catch.

FWIW, IIRC when converting to or from seconds LC takes into account the local system's GMT offset per RFC 2822, so "the seconds" is always GMT and conversions should work independent of time zones.

The only other date format in LC that preserves GMT offset is "the internet date", but while it's great for logging and such it's often too long for display to the user and more cumbersome to parse than other formats it can be easily converted to.

[richmond62]

date.png (4.88 KiB) Viewed 8129 times

Just to point out that LiveCode uses the
North American date format: MM/DD/YY
so this is 11th December 2016 and
NOT 12th November 2016.

[MaxV]

How Do I Find Number of Days between 2 Dates?

So I have been beating my head against a wall for almost 3 hours, trying not to bother anyone on the forum. I looked at several instructions in the dictionary, but I have not found a way to get the number of days between 2 different dates.

Thanks,

David

Very very easy:

Code: Select all

put libDate_DaysBetween( pYear1,pMonth1,pDay1,pYear2,pMonth2,pDay2)

Just install the libdate library: https://raw.githubusercontent.com/anger ... ate.script

Propose changes on https://github.com/angerangel/libdate/b ... ate.script

[DR White]

Max,

Thanks for guiding me to this library. I will give it a try latter. I have coded a work-around currently.

Thanks again for your help,

David