adding the date into a file name 
Adding the date into a file name helps record system information or provides a backup based on date.  
Using the year first allows for easier sorts when you have several files with the same name.

This command:  ifconfig -a >   network.`date +'%Y_%m_%d'`.txt
produces this: 		network.2014_07_23.txt

This command:  ifconfig -a >   `date +'%Y_%m_%d'`-network.txt
produces this: 		2014_07_23-network.txt


--> more 2014_12_23-network.txt

lan0      Link encap:Ethernet  HWaddr 11:11:11:11:11:11  
          inet addr:11.111.11.111  Bcast:11.111.11.111  Mask:111.111.111.111
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:58541560 errors:0 dropped:0 overruns:0 frame:0
          TX packets:55809888 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:46141382968 (44003.8 Mb)  TX bytes:55666523858 (53087.7 Mb)
          Interrupt:16 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:196167 errors:0 dropped:0 overruns:0 frame:0
          TX packets:196167 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:16439051 (15.6 Mb)  TX bytes:16439051 (15.6 Mb)



You could create backup copies manually by typing:
	 cp /etc/passwd `date +'%Y_%m_%d'`-etc-passwd.txt
					output:		2014_12_23-etc-passwd.txt
	 cp /etc/group `date +'%Y_%m_%d'`-etc-group.txt
					output:		2014_12_23-etc-group.txt
	 cp /etc/hosts `date +'%Y_%m_%d'`-etc-hosts.txt
					output:		2014_12_23-etc-hosts.txt


A script could be written to backup a list of files and it could be run periodically via a cronttab.