Thanks for the script!
Although, I cannot get it to work. Something to do with the system time?

./letsencrypt-expiring-certs -expire="date"

2016/03/23 16:50:35 parsing time "wo mrt 23 16:50:35 CET 2016" as "Mon Jan _2 15:04:05 MST 2006": cannot parse "wo mrt 23 16:50:35 CET 2016" as "Mon"

./letsencrypt-expiring-certs -expire="date --date='2 weeks'"

2016/03/23 16:50:47 parsing time "wo apr 6 17:50:47 CEST 2016" as "Mon Jan _2 15:04:05 MST 2006": cannot parse "wo apr 6 17:50:47 CEST 2016" as "Mon"

./letsencrypt-expiring-certs -expire="date --date '03/05/2016 11:28'"

2016/03/23 16:50:52 parsing time "za mrt 5 11:28:00 CET 2016" as "Mon Jan _2 15:04:05 MST 2006": cannot parse "za mrt 5 11:28:00 CET 2016" as "Mon"

uname -a

Linux vps 4.3.0-0.bpo.1-amd64 #1 SMP Debian 4.3.5-1~bpo8+1 (2016-02-23) x86_64 GNU/Linux

locale

LANG=nl_NL
LANGUAGE=
LC_CTYPE="nl_NL"
LC_NUMERIC="nl_NL"
LC_TIME="nl_NL"
LC_COLLATE="nl_NL"
LC_MONETARY="nl_NL"
LC_MESSAGES="nl_NL"
LC_PAPER="nl_NL"
LC_NAME="nl_NL"
LC_ADDRESS="nl_NL"
LC_TELEPHONE="nl_NL"
LC_MEASUREMENT="nl_NL"
LC_IDENTIFICATION="nl_NL"
LC_ALL=

cat /etc/issue.net

Debian GNU/Linux 8