This is the most robust solution for inter-form collaboration: implementing appropriate interface by the form class.
Please see my past answer:
How to copy all the items between listboxes in two forms
Some notes: you suffer from such a dirty code. The names like "label1", "label2" violate (good) Microsoft naming conventions. You should never leave Designer-generated names, rename them to some semantic names. Using times in most cases is quite a bad idea. Prefer thread to stay out of trouble. (See, for example, my past answer here: Timer Threading in C#