A device that can be set for a number of minutes (usually up to one hour) that sounds an alarm such as a bell or buzzer when the specified amount of time has elapsed; commonly used when cooking or baking.
If you tend to get sidetracked, set a small kitchen timer by the computer to give you a quick reminder to save your work.
Set a kitchen timer to go off every 15 minutes, and write down in your notebook exactly what you spent the previous 15 minutes doing.
Use a kitchen timer to hold you to your schedule and remind you when it's time to move on to the next task.
Now set a kitchen timer or alarm clock and return to your observation once an hour or once every two hours until dinnertime, marking down how much light the spot in the garden receives.