Hiding factual information can lead to a ban. They may not verify information at that point, but if it's ever discovered that you have hidden information, you will loose everything.
Based on travel history they decide if you need police certificate. So there are potential consequences to the application if you hide this information.
It's better to be approximate. Try remembering seasons or festivals when you went and came. If you think you worked in a country for 2 years, be approximate but put the information.