Do you have a problem estimating time? For example, how long it will take to do something, or getting something finished in a fixed time? Start ‘clocking’ time.
That means timing how long you are busy with a task. You will be surprised! In general, things take 1/3 to a half as much time again as you expect. If you have timed yourself, you will probably allow more time or be more realistic with your planning.
What can also help is to have a visible analogue clock nearby at all times. A digital clock (numbers only) does not give you a sense of time passing in the way that an analogue clock face does.
Do you use a timer because your child or pupil wants to learn to concentrate? In general, people tend to set the timer to a round figure of 10 or 20 minutes. However, according to Leslie Josel, who recently gave a presentation about the working of the ADHD brain in London, it works better if you set the timer to 17 or 33 minutes, for example. These numbers are more of a challenge, and more fun. Give it a go!