Meditation is a personal choice. There are many types, offering different results. I do transcendental meditation and in my case there is one thing I find which takes away from my experience and enjoyment of the process. And that is the clock watching.
It is suggested that you do 20 minutes in the morning and 20 minutes in the evening. This is easy. Almost everyone can spare 40 minutes in their day. It is just that when you are in the process of meditating you can be worrying how long you have been meditating and therefore your mind is elsewhere.
I came across an app for ‘i’ devices named TMTimester and it is a ripper. Just set it, start meditating and stop thinking. Give it a try. Obviously it can be used to time anything you like. Even to make the perfect egg. But for meditation, I reckon it is a must.
I can’t vouch for these but here are some similar apps for Android
Android alternative 1
Android alternative 2