To wipe out a disk so "Disk Utility" will earase and start over use:

	sudo gpt destroy -r /dev/disk2


Time Machine Options

	Format
		Mac OS Extended (Journaled)
		Mac OS Extended (Case-sensitive, Journaled)		USING THIS
		Ex Fat			(For partitions greater than 32Gb)
		MS-DOS (FAT)

	Scheme
		GUID Partition Map		USING THIS
		Master Boot Record		(used with Ex FAT and MS-DOS (FAT))
		Apple Partition Map		(used with old PowerPC)

https://support.apple.com/kb/PH22240?locale=en_US