DATE
Get current date in seconds since the epoch (1970-01-01 00:00:00 UTC) 
$ date '+%s'
1339832819
Convert a date specified using ISO 8601 into a number of seconds since the epoch (1970-01-01 00:00:00 UTC) : 
$ date -d '2012-02-25' '+%s'
1330124400

$ date -d '2012-02-25 06:26:57' '+%s'
1330147617
Convert a date specified using common U.S. writing into a number of seconds since the epoch (1970-01-01 00:00:00 UTC) : 
$ date -d '02/25/12' '+%s'
1330124400
Convert a date in seconds since the epoch (1970-01-01 00:00:00 UTC) into a standard date format : 
$ date -d '@1339832819'
Sat Jun 16 09:46:59 CEST 2012
Convert a date in seconds since the epoch (1970-01-01 00:00:00 UTC) into a specified format : 
$ date -d '@1339832819' '+%Y-%m-%d %H:%M:%S'
2012-06-16 09:46:59
GETENT
Get passwd entry for a specified login name : 
$ getent passwd root
root:x:0:0:root:/root:/bin/bash
TOP
Show threads with "top" : 
$ top
H
VIM
Activate syntax highlighting : 
:syntax on
Activate highlighting for searched strings : 
:se hlsearch
Deactivate highlighting for searched strings : 
:nohl