Page 1 of 1
How to know whether a dateItem is before or after another?
Posted: Tue Apr 15, 2014 8:11 pm
by Mag
Naturally this don't work...
Code: Select all
convert date1 to dateItems
convert date2 to dateItems
if date2 > date1 then
answer "date1 is before than date2"
end if
Re: How to know whether a dateItem is before or after anothe
Posted: Tue Apr 15, 2014 8:31 pm
by bangkok
Convert your 2 dates... in seconds.
And then you can compare.
Re: How to know whether a dateItem is before or after anothe
Posted: Wed Apr 16, 2014 4:29 am
by dunbarx
Hi.
What Bangkok said.
But this works as well:
Code: Select all
on mouseUp
put "5/9/94" into d1
put "5/9/95" into d2
convert d1 to dateItems
convert d2 to dateItems
if d2 > d1 then answer "date1 is before date2"
else answer "date2 is before date1"
end mouseUp
What did not for you?
Craig Newman
Re: How to know whether a dateItem is before or after anothe
Posted: Wed Apr 16, 2014 8:28 am
by Mag
Thank you for your post bangkok.
Hi Craig, I realized that I was doing the conversion in the wrong place. Thank you.
Can I then make a date converted to dateitems, to seconds with convert command or it's necessary to construct the date using items?
Re: How to know whether a dateItem is before or after anothe
Posted: Wed Apr 16, 2014 9:06 am
by Mag
I done some more tests and I'm not sure that when you compare dateItems, it compares dates, maybe it compares something else, so:
2014,4,16,10,3,15,4 < 2014,4,16,9,34,50,4
Re: How to know whether a dateItem is before or after anothe
Posted: Wed Apr 16, 2014 11:47 am
by Klaus
What exactly would you exspect when you try to compare 2 STRINGS instead of two (single) numbers?
...
put ("Klaus" < "Mag")
## -> TRUE
## Whatever that means
...
Re: How to know whether a dateItem is before or after anothe
Posted: Wed Apr 16, 2014 2:30 pm
by dunbarx
Hi.
What exactly would you expect when you try to compare 2 STRINGS instead of two (single) numbers?
Did you get what Klaus meant? (And what I said?) He makes a very important point.
It is almost a kluge that dateItems can be compared this way. The order of items: year,month,day,24 hour time, etc, allows the string comparison to work in a date comparison way. All because the order of items in that keyword makes sense in an ever-decreasing series of values that refine an instant of time. This may actually have been done on purpose, back in 1987.
The one item in that string that might throw a monkey wrench into the mix is the last item, the day-of-week. But that last item will never be counted, since earlier ones will already have made their "choice".
Craig
Re: How to know whether a dateItem is before or after anothe
Posted: Wed Apr 16, 2014 2:45 pm
by FourthWorld
In addition to easy comparison, another benefit to storing time stamps as seconds is that they're independent of time zones, being the number of seconds elapsed since Jan 1 1970 GMT.
So when doing conversions to human-readable formats, the output represents the time in a form appropriate for the local machine. This can be very valuable for groupware applications where team members may be in different time zones.
The only human-readable date/time format that's time-zone-independent in LC is internet date, e.g.:
Wed, 16 Apr 2014 06:42:02 -0700
Conversions on internet date format will also be presented in local time, thanks to the GMT offset it includes. But of course since that string begins with the week day it's not a good choice for comparison, and if you have a lot of data the more compact form of seconds will save a little space as well.
Re: How to know whether a dateItem is before or after anothe
Posted: Wed Apr 16, 2014 4:48 pm
by Mag
Thank you guys, because of the possibility of make date calculations with dateItems, I was erroneous think that that variable it had some magical status.
Code: Select all
on mouseUp
convert the date to dateItems
put it into field 1 -- 2014,4,16,0,0,0,4
add 23 to item 3 of it
put it into field 2 -- 2014,4,39,0,0,0,4
convert it to date
put it into field 3 -- 5/9/14
end mouseUp
Ah, what a fool I've been, nothing works in this way in RevTalk (By the way, this is correct definition of the language?). As noted by Klaus, a string is just a string... Now I understand that the magic is due by the nature of the convert command, and not by some special property of the dateItem-generated strings (thank you Klaus
)
As suggested by FourthWorld, I will go just with (clear, simple, comparable, beautiful) seconds!
PS
I Craig, I think I misunderstood your code, above, on the comparison, sorry for the confusion
