Clock and calendar time spent on your business is NOT deductible! But Time tracking is necessary for record keeping purposes.
For example, as you track your various business activities you can make sure you have captured the deductions for money spent on business expenses and miles driven while performing those activities. Using a calendar feature this way can prompt you for more deductions that would otherwise get missed.
This is particularly helpful if you are working your business less than full time as it helps you to establish that you are working your business regularly and consistently. The IRS usually considers time spent working your business as one of the elements to establish whether or not your business is a legitimate business or simply a hobby.