Currently I am building bash based toolkit to troubleshoot and analyze SSL certificats and certificate requests.
In favour of that I had to fiddle around with date and ran into a confusing problem. Let me show you an example:
$ date -j -f '%b %d %T %Y %Z' 'Aug 7 07:09:42 2014 GMT' +%s
1407395382
$ date -j -f '%b %d %T %Y %Z' 'Oct 27 17:35:57 2013 GMT' +%s
Failed conversion of ``Oct 27 17:35:57 2013 GMT'' using format ``%b %d %T %Y %Z''
date: illegal time format
usage: date [-jnu] [-d dst] [-r seconds] [-t west] [-v[+|-]val[ymwdHMS]] ...
[-f fmt date | [[[mm]dd]HH]MM[[cc]yy][.ss]] [+format]
As you can see the first statement returned our timestamp without any problem, but the second one fails with a date: illegal time format message. Why is that? The answer is rather simple: month and day representations have to be your in system's nationality/language!
So if you change the Oct to Okt (i am running a german OS X), the conversion works without ay problems.
How to solve this?
Either you change your date informations to the systems nationality, or you do this simple trick:
$ LANG=C date -j -f '%b %d %T %Y %Z' 'Oct 27 17:35:57 2013 GMT' +%s
1382895357
Puting a LANG=C infront of the command tells date to act normal and not OS X-like so you dont run into this problem as well.
Credits to drkshadow out of the #bash who assisted me here.