The easiest way to perform days count since a specifics day is to first get a number of seconds<\/p>\n
since epoch time ( 1970-01-01 ) for both dates. As an example let\u2019s count number of days<\/p>\n
since 28.12.1999 until today 8.1.2018. Consider a following example:<\/p>\n
$ echo $((($(date +%s)-$(date +%s –date “1999-12-28”))\/(3600*24))) days
\n6586 days<\/p>\n
Let’s add little bit of readability to the above command by using variables. First, we get<\/p>\n
seconds since epoch time ( 1970-01-01 ) until now:<\/p>\n
$ now=$(date +%s)<\/p>\n
$ echo $now
\n1515370378<\/p>\n
Next we do the same for the 28.12.1999 date:<\/p>\n
past=$(date +%s –date “1999-12-28”)
\n$ echo $past
\n946299600<\/p>\n
Next, calculate the difference:<\/p>\n
$ difference=$(($now-$past))
\n$ echo $difference
\n569070778<\/p>\n
Lastly, convert the difference in seconds to days:
\n$ echo $(($difference\/(3600*24)))
\n6586<\/p>\n
All done. The same principle can be used to calculate days between any specific days.<\/p>\n
For example let’s count days between 1.1.2016 and 31.12.2016 dates:<\/p>\n
$ echo $((($(date +%s –date “2016-12-31”)-$(date +%s –date “2016-1-1”))\/(3600*24))) days
\n365 days<\/p>\n
<\/p>\n