Topic: Deduct Dates in Autolisp

[@_Bilal]

Hi Guys,

Is there an AutoLISP routine to deduct two dates and get the results in days
for example: last date is  "19750225"  year 1975 month 02 day 25 and the current date is (rtos (getvar "cdate") 2 0)
The question is how to get the exact days between this 2 dates in autolisp.

Thanks

[Lee Mac]

Convert the dates to Julian then subtract, e.g.:

Code - Auto/Visual Lisp: [Select]

1. (defun daydiff ( d1 d2 )
2.     (- (fix (dtoj d2)) (fix (dtoj d1)))
3. )

Code - Auto/Visual Lisp: [Select]

1. _$ (daydiff 20190117 (getvar 'cdate))
2. 2
3. _$ (daydiff 20181219 (getvar 'cdate))
4. 31

(dtoj is part of Julian.lsp included with Express Tools)

Note that the DATE system variable returns a Julian date already, so if you simply want the difference from the current date, the code may be:

Code - Auto/Visual Lisp: [Select]

1. (defun daydiffnow ( d1 )
2.     (- (fix (getvar 'date)) (fix (dtoj d1)))
3. )

Code - Auto/Visual Lisp: [Select]

1. _$ (daydiffnow 20190117)
2. 2

[@_Bilal]

Thank you Lee Mac.