As our children grow day by day, there are many small changes that we may not notice; using a diary can help you observe and identify change over a longer period. Observational diaries are a good instrument for observing and monitoring over a long period. Simply keeping a diary of what you do each day will highlight long term changes in development because when you compare entries weeks or months apart, you will see that your little ones are undertaking activities that were previously beyond their capabilities.
Diaries are a useful tool to explore long term concerns that you have, for example, to help identify what triggers certain physical conditions or behavioural patterns in your child. If your child is prone to allergies, you might want to log what they eat, where you have been during the day, what the weather was like and how their allergies were manifested. Over time you might pick out certain triggers such as food types, weather patterns or locations. By isolating the causes you can then learn to avoid them.
If your children are cared for by childminders during the day then you should ask them to undertake monitoring for you, and to keep a regular diary. ToucanLearn offers a Daily Diary which can be used for such purposes, fill entries in regularly and then look through them every couple of weeks in order to try to ascertain what you are looking for.