Formato de fechas
Format/result | Command --------------------------------+---------------------------- YYYY-MM-DD_hh:mm:ss | date +%F_%T YYYYMMDD_hhmmss | date +%Y%m%d_%H%M%S YYYYMMDD_hhmmss (UTC version) | date --utc +%Y%m%d_%H%M%SZ YYYYMMDD_hhmmss (with local TZ) | date +%Y%m%d_%H%M%S%Z YYYYMMSShhmmss | date +%Y%m%d%H%M%S YYYYMMSShhmmssnnnnnnnnn | date +%Y%m%d%H%M%S%N YYMMDD_hhmmss | date +%y%m%d_%H%M%S Seconds since UNIX epoch: | date +%s Nanoseconds only: | date +%N Nanoseconds since UNIX epoch: | date +%s%N ISO8601 UTC timestamp | date --utc +%FT%TZ ISO8601 UTC timestamp + ms | date --utc +%FT%T.%3NZ ISO8601 Local TZ timestamp | date +%FT%T%Z ISO8601 Para MongoDB | date +"%Y-%m-%dT%H:%M:%S%z"

Ver una fecha que viene en formato raro
date -d 2017-11-06T08:50:40-0300

Convertir fecha a formato raro
date -d "2017-11-21 12:00:00" +"%Y-%m-%dT%H:%M:%S%z"