vecka-cli
Som vecka.nu fast i terminal
$ npm install vecka-cli -g
usage example
$ vecka
11
vecka
followed by a number (week) gives you the date range of that week for current year:
$ vecka 11
Mon Mar 14 2016 - Sun Mar 20 2016
vecka
followed by a date returns week of that date.
$ vecka 2016-03-14
11