jdate.gms : Julian date test
The gams function JDate(year,month,day) accepts arguments similar to
to date functions in other languages. The earliest date is Jan 1, 1, and
the latest date is Dec 31, 9999. Gams picked Jan 1, 1900 as day 1,
as done by Excel. Unfortunately, Excel treats the year 1900 incorrectly
as a leap year and the serial days starting with March 1, 1900 will
be off by one day.
The arguments are can be positive or negative and do not have to form
a proper date. The arguments with fractional values are first converted
to a signed integer by using the floor() function.
Note about Excel:
The Excel DATE(year,month,day) function has the following data ranges
note that excel incorrectly treats the year 1900 as a leap year.
DATE(1900, 1, 1) = 1 incorrect should be 2
DATE(1900, 2,28) = 59 incorrect should be 60
DATE(1900, 3, 1) = 61
DATE(9999,12,31) = 2958465
for years having a value of less than 1900, 1900 + year is assumed
The following table shows different ways of entering dates:
Reference:
- GAMS Development Corporation, Formulation and Language Example.
Small Model of Type: GAMS
<![CDATA[
$title Julian date test (JDATE,SEQ=292)
* The gams function JDate(year,month,day) accepts arguments similar to
* to date functions in other languages. The earliest date is Jan 1, 1, and
* the latest date is Dec 31, 9999. Gams picked Jan 1, 1900 as day 1,
* as done by Excel. Unfortunately, Excel treats the year 1900 incorrectly
* as a leap year and the serial days starting with March 1, 1900 will
* be off by one day.
*
* The arguments are can be positive or negative and do not have to form
* a proper date. The arguments with fractional values are first converted
* to a signed integer by using the floor() function.
*
* Note about Excel:
* The Excel DATE(year,month,day) function has the following data ranges
* note that excel incorrectly treats the year 1900 as a leap year.
* DATE(1900, 1, 1) = 1 incorrect should be 2
* DATE(1900, 2,28) = 59 incorrect should be 60
* DATE(1900, 3, 1) = 61
* DATE(9999,12,31) = 2958465
* for years having a value of less than 1900, 1900 + year is assumed
*
* The following table shows different ways of entering dates:
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set i / 1*22/; acronym error
table tvals(i,*) test values
year month day excel gams
1 2005 10 20 38645
2 2005.3 10.3 20.3 38645
3 2005.7 10.7 20.7 38645
4 2005 22 20 39010
5 2005 22 300 39290
6 2005 -5 300 38468
7 2005 -5 -10 38158
8 2005 -5 -10.3 38157
9 2005 -5 -10.7 38157
10 2 -9 -424 0 // excel 1900 0 1 must be wrong
11 1900 1 1 1
12 0 0 1 error
13 2004 2 30 38047
14 2004 14 30 38413
15 2004 0 0 37955
16 9999 12 31 2958465
17 9999 13 1 error
18 1900 1 2 2
19 1899 12 31 693962 // excel 3799 12 31
20 1899 12 30 693961 // excel 3799 12 30
21 1900 2 1 32
22 1 1 1 367 // excel 1901 1 1
parameter res(i) gams julian serial numbers;
res(i) = jdate(tvals(i,'year'),tvals(i,'month'),tvals(i,'day'));
tvals(i,'gams') = res(i); display tvals;
* Now we will recover the date components
parameter back(i,*) recovered date components;
back(i,'gams') = res(i);
back(i,'year') = gyear(res(i));
back(i,'month') = gmonth(res(i));
back(i,'day') = gday(res(i));
back(i,'new') = jdate(back(i,'year'),back(i,'month'),back(i,'day'));
display back;
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