Rename Image File Name to Date-Time format

Earlier I had tried the command line tool like exiv2 to rename image file name. I had put down the steps to do so in this blog itself at Picasa: Renaming File Names to Picasa Captions.
Now I see a nice option in IrfanView to do so easily using GUI.
In Irfanview:

1. Press B or File -> Batch Conversion/Rename
2. On the top left menu, under Work As, select Batch Rename 
3. In the name pattern textbox, put in $T(%Y%m%d_%H%M%S) to get image names in standard format of YYYYMMDD_HHMMSS. You can try other formats as well.
4. Select files to be renamed and do Start Batch

Irfanview Batch Rename

And its done :)